Twitter, Inc. v. Taamneh

P R E L I M I N A R Y P R I N T
Volume 598 U. S. Part 2
Pages 471–507
OFFICIAL REPORTS
OF
T H E S U P R E M E C O U R T
May 18, 2023
REBECCA A. WOMELDORF
reporter of decisions
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N O T I C E : This preliminary print is subject to formal revision before
the bound volume is published. Users are requested to notify the Reporter
of Decisions, Supreme Court of the United States, Washington, D.C. 20543,
pio@supremecourt.gov, of any typographical or other formal errors.

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TWITTER, INC. v. TAAMNEH et al.
certiorari
to the united states court of appeals for
the ninth circuit
No. 21–1496. Argued February 22, 2023—Decided May 18, 2023
In 2017, Abdulkadir Masharipov carried out a terrorist attack on the Reina
nightclub in Istanbul, Turkey, on behalf of the Islamic State of Iraq and
Syria (ISIS), a designated Foreign Terrorist Organization. Masharipov
killed Nawras Alassaf and 38 others. Alassaf 's family then brought
this suit under 18 U. S. C. § 2333, an Antiterrorism Act (ATA) provision
that permits U. S. nationals who have been “injured . . . by reason of an
act of international terrorism” to fle a civil suit for damages. Instead
of suing ISIS directly under § 2333(a), the plaintiffs (respondents here)
invoked § 2333(d)(2) to sue three of the largest social-media companies
in the world—Facebook, Twitter (petitioner here), and Google (which
owns YouTube)—for aiding and abetting ISIS.
The parties today agree on the basic aspects of these platforms: Bil-
lions of people from around the world have signed up for them and
upload massive amounts of content each day. Defendants proft from
that content by placing advertisements on or near it and use “recom-
mendation” algorithms that match content, advertisements, and users
based on information about the use, advertisement, and content being
viewed. As the parties represent things, the algorithms here match
any content with any user who is more likely to view that content, and
the platforms perform little to no front-end screening on any content
before it is uploaded.
Plaintiffs, however, allege that for several years the companies have
knowingly allowed ISIS and its supporters to use their platforms and
“recommendation” algorithms as tools for recruiting, fundraising, and
spreading propaganda; plaintiffs further allege that these companies
have, in the process, profted from the advertisements placed on ISIS'
tweets, posts, and videos. The District Court dismissed the complaint
for failure to state a claim, but the Ninth Circuit reversed.
Held: Plaintiffs' allegations that these social-media companies aided and
abetted ISIS in its terrorist attack on the Reina nightclub fail to state
a claim under 18 U. S. C. § 2333(d)(2). Pp. 482–507.
(a) In 2016, Congress enacted the Justice Against Sponsors of Terror-
ism Act (JASTA) to impose secondary civil liability on anyone “who
aids and abets, by knowingly providing substantial assistance, or who
conspires with the person who committed such an act of international

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terrorism.” § 2333(d)(2). The question here is whether the conduct of
the
social-media company defendants gives rise to aiding-and-abetting
liability for the Reina nightclub attack. Pp. 482–484.
(b) The text of JASTA begs two questions: What does it mean to “aid
and abet”? And, what precisely must the defendant have “aided and
abetted”? Pp. 484–497.
(1) Nothing in the statute defnes any of the critical terms in the
phrase “aids and abets, by knowingly providing substantial assistance.”
The term “aids and abets,” however, is a familiar common-law term and
thus presumably “brings the old soil” with it. Sekhar v. United States,
570 U. S. 729, 733. Congress also provided additional context in JASTA
by pointing to Halberstam v. Welch, 705 F. 2d 472, as “provid[ing] the
proper legal framework” for “civil aiding and abetting and conspiracy
liability.” 130 Stat. 852. Halberstam's legal framework, viewed in
context of the common-law tradition from which it arose, confrms that
“aids and abets” in § 2333(d)(2) refers to a conscious, voluntary, and cul-
pable participation in another's wrongdoing. Pp. 485–493.
(i) In Halberstam, the D. C. Circuit undertook an extensive sur-
vey of the common law with respect to aiding and abetting and synthe-
sized the surveyed cases as resting on three main elements: (1) there
must be a wrongful act causing an injury performed by the person
whom the defendant aided; (2) at the time assistance was provided, the
defendant must have been “generally aware of his role as part of an
overall illegal or tortious activity;” and (3) the defendant must have
“knowingly and substantially assist[ed] the principal violation.” 705
F. 2d, at 477. The court then articulated six factors to help determine
whether a defendant's assistance was “substantial.” They are (1) “the
nature of the act assisted,” (2) the “amount of assistance” provided, (3)
whether the defendant was “present at the time” of the principal tort,
(4) the defendant's “relation to the tortious actor,” (5) the “defendant's
state of mind,” and (6) the “duration of the assistance” given. Id.,
at 488 (emphasis deleted). Halberstam also clarifed that those who aid
and abet “a tortious act may be liable” not only for the act itself but
also “for other reasonably foreseeable acts done in connection with it.”
Id., at 484. Finally, the court warned that its formulations should “not
be accepted as immutable components” but should be “adapted as new
cases test their usefulness in evaluating vicarious liability.” Id., at 489.
Pp. 485–487.
(ii) Because the allegations here—involving international terror-
ist networks and world-spanning internet platforms—are a far cry from
the facts of Halberstam, the Court must ascertain the basic thrust of
Halberstam's elements to determine how to adapt them to the facts of
this case. To do so, the Court turns to the common law of aiding and

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abetting upon which Halberstam rested, and to which JASTA's common-
law
terminology points. At common law, the basic “view of culpability”
animating aiding and abetting liability is that “a person may be respon-
sible for a crime he has not personally carried out if he helps another to
complete its commission.” Rosemond v. United States, 572 U. S. 65, 70.
However, the concept of “helping ” in the commission of a crime or a
tort has never been boundless and ordinarily requires some level of
blameworthy conduct; those limits ensure that aiding and abetting does
not sweep in mere passive bystanders or those who, for example, simply
deliver mail that happens to aid criminals. In tort law, many cases
have thus required a voluntary, conscious, and culpable participation in
the wrongful conduct to establish aiding and abetting. In doing so,
they further articulated Halberstam's framework to capture those lim-
its. As above, that framework requires that the defendant give know-
ing and substantial assistance to the primary tortfeasor; notably, courts
often viewed those twin requirements as working in tandem, with a
lesser showing of one demanding a greater showing of the other to es-
tablish a conscious, culpable participation in the tort. Pp. 487–492.
(iii) Halberstam differentiated types of aid along the same culpa-
bility axis that grounded the common law. And its six factors for “sub-
stantial assistance” call for the same balancing that courts had under-
taken previously between the nature and amount of assistance and the
defendant's scienter. Pp. 492–493.
(2) The parties then vigorously dispute what precisely a defendant
must aid and abet under § 2333(d)(2). Plaintiffs assert that it is “the
person,” while defendants insist that it is the “act of international ter-
rorism.” That syntactic dispute makes little difference here, because
aiding and abetting is inherently a rule of secondary liability for specifc
wrongful acts. In the tort context, liability is imposed only when some-
one commits (not merely agrees to commit) an actual tort. And in this
case, the ATA limits that liability to injuries caused by an “act of inter-
national terrorism,” § 2333(a). It thus is not enough for a defendant
to have given substantial assistance to a transcendent enterprise. A
defendant must have aided and abetted (by knowingly providing sub-
stantial assistance) another person in the commission of the actionable
wrong—here, an act of international terrorism. However, that does not
require a strict nexus between the assistance and the wrongful act; de-
fendants are liable for other torts that are the foreseeable risk of an
intended tort, and an aider and abettor can assist someone without
knowing all the details of his plan. Plus, in appropriate circumstances,
a defendant's role in an illicit enterprise can be so systemic and inten-
tional that the defendant aids and abets each act of the enterprise—as
in Halberstam itself.

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To summarize the requirements of § 2333(d)(2), the phrase “aids and
abets,
by knowingly providing substantial assistance” points to the ele-
ments and factors articulated by Halberstam. Those elements and fac-
tors should not be taken as infexible codes but should be understood in
light of the common law and applied as a framework designed to hold
defendants liable when they consciously and culpably “participate[d] in”
a tortious act in such a way as to help “make it succeed.” Nye & Nissen
v. United States, 336 U. S. 613, 619. Pp. 493–497.
(c) Plaintiffs have satisfed Halberstam's frst two elements by alleg-
ing both that ISIS committed a wrong and that defendants knew they
were playing some sort of role in ISIS' enterprise. But plaintiffs' alle-
gations do not show that defendants gave such knowing and substantial
assistance to ISIS that they culpably participated in the Reina attack.
Pp. 497–506.
(1) Plaintiffs allege that defendants aided and abetted ISIS in the
following ways: First, they provided social-media platforms, which are
generally available to the internet-using public; ISIS was able to upload
content to those platforms and connect with third parties on them.
Second, defendants' recommendation algorithms matched ISIS-related
content to users most likely to be interested in that content. And,
third, defendants knew that ISIS was uploading this content but took
insuffcient steps to ensure that its content was removed. Plaintiffs do
not allege that ISIS or Masharipov used defendants' platforms to plan
or coordinate the Reina attack. Nor do plaintiffs allege that defendants
gave ISIS any special treatment or words of encouragement. Nor is
there reason to think that defendants carefully screened any content
before allowing users to upload it onto their platforms.
None of plaintiffs' allegations suggest that defendants culpably “asso-
ciate[d themselves] with” the Reina attack, “participate[d] in it as some-
thing that [they] wishe[d] to bring about,” or sought “by [their] action
to make it succeed.” Nye & Nissen, 336 U. S., at 619 (internal quota-
tion marks omitted). Defendants' mere creation of their media plat-
forms is no more culpable than the creation of email, cell phones, or the
internet generally. And defendants' recommendation algorithms are
merely part of the infrastructure through which all the content on their
platforms is fltered. Moreover, the algorithms have been presented as
agnostic as to the nature of the content. At bottom, the allegations
here rest less on affrmative misconduct and more on passive nonfea-
sance. To impose aiding-and-abetting liability for passive nonfeasance,
plaintiffs must make a strong showing of assistance and scienter.
Plaintiffs fail to do so.
First, the relationship between defendants and the Reina attack is
highly attenuated. Plaintiffs make no allegations that defendants' rela-

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tionship with ISIS was signifcantly different from their arm's length,
passive
, and largely indifferent relationship with most users. And their
relationship with the Reina attack is even further removed, given the
lack of allegations connecting the Reina attack with ISIS' use of these
platforms. Second, plaintiffs provide no reason to think that defend-
ants were consciously trying to help or otherwise participate in the
Reina attack, and they point to no actions that would normally support
an aiding-and-abetting claim.
Plaintiffs' complaint rests heavily on defendants' failure to act; yet
plaintiffs identify no duty that wou ld require defendants or other
communication-providing services to terminate customers after dis-
covering that the customers were using the service for illicit ends.
Even if such a duty existed in this case, it would not transform defend-
ants' distant inaction into knowing and substantial assistance that could
establish aiding and abetting the Reina attack. And the expansive
scope of plaintiffs' claims would necessarily hold defendants liable as
having aided and abetted each and every ISIS terrorist act committed
anywhere in the world. The allegations plaintiffs make here are not
the type of pervasive, systemic, and culpable assistance to a series of
terrorist activities that could be described as aiding and abetting each
terrorist act by ISIS.
In this case, the failure to allege that the platforms here do more
than transmit information by billions of people—most of whom use the
platforms for interactions that once took place via mail, on the phone,
or in public areas—is insuffcient to state a claim that defendants know-
ingly gave substantial assistance and thereby aided and abetted ISIS'
acts. A contrary conclusion would effectively hold any sort of commu-
nications provider liable for any sort of wrongdoing merely for knowing
that the wrongdoers were using its services and failing to stop them.
That would run roughshod over the typical limits on tort liability and
unmoor aiding and abetting from culpability. Pp. 498–503.
(2) The Ninth Circuit's analysis obscured the essence of aiding-and-
abetting liability. First, the Ninth Circuit framed the issue of substan-
tial assistance as turning on defendants' assistance to ISIS' activities in
general, rather than with respect to the Reina attack. Next, the Ninth
Circuit misapplied the “knowing ” half of “knowing and substantial as-
sistance,” which is designed to capture the defendants' state of mind
with respect to their actions and the tortious conduct (even if not always
the particular terrorist act). Finally, the Ninth Circuit appears to have
regarded Halberstam's six substantiality factors as a sequence of dispar-
ate, unrelated considerations without a common conceptual core. In
doing so, the Ninth Circuit focused primarily on the value of defendants'
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platforms to ISIS, rather than whether defendants culpably associated
themselves
with ISIS' actions. Pp. 503–505.
(3) There is also one set of allegations specifc to Google: that
Google reviewed and approved ISIS videos on YouTube as part of a
revenue-sharing system and thereby shared advertising revenue with
ISIS. But the complaint here alleges nothing about the amount of
money that Google supposedly shared with ISIS, the number of accounts
approved for revenue sharing, or the content of the videos that were
approved. Nor does it give any other reason to view Google's revenue
sharing as substantial assistance. Without more, plaintiffs thus have
not plausibly alleged that Google knowingly provided substantial assist-
ance to the Reina attack, let alone (as their theory of liability would
require) every single terrorist act committed by ISIS. Pp. 505–506.
(d) The concepts of aiding and abetting and substantial assistance do
not lend themselves to crisp, bright-line distinctions. Applying the
guideposts provided by the common law and Halberstam, the nexus be-
tween defendants and the Reina attack is far removed. As alleged by
plaintiffs, defendants designed virtual platforms and knowingly failed
to do “enough” to remove ISIS-affliated users and ISIS-related content
from their platforms. Yet, plaintiffs have failed to allege that defend-
ants intentionally provided any substantial aid to the Reina attack or
otherwise consciously participated in it—much less that defendants so
pervasively and systemically assisted ISIS as to render them liable for
every ISIS attack. Plaintiffs accordingly have failed to state a claim
under § 2333(d)(2). Pp. 506–507.
2 F. 4th 871, reversed.
Thomas, J., delivered the opinion for a unanimous Court. Jackson, J.,
fled a concurring opinion, post, p. 507.
Seth P. Waxman argued the cause for petitioner. With
him on the briefs were Patrick J. Carome, Ari Holtzblatt,
Claire H. Chung, Amy Lishinski, Andres C. Salinas, and
Nathaniel W. Reisinger. Paul D. Clement fled briefs for
respondents Facebook, Inc., et al. supporting petitioner
under this Court's Rule 12.6. With him on the briefs were
Erin E. Murphy, Theodore J. Boutrous, Jr., Helgi C. Walker,
Jonathan C. Bond, Jacob T. Spencer, Lisa S. Blatt, Sarah M.
Harris, Aaron Z. Roper, Brian M. Willen, Steffen N. John-
son, Lauren Gallo White, Cassandra Knight, Nora Puckett,
and Jennifer Newstead.
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Deputy Solicitor General Kneedler argued the cause for
the
United States as amicus curiae urging reversal. With
him on the brief were Acting Solicitor General Fletcher,
Deputy Assistant Attorney General Granston, Erica L.
Ross, and Sharon Swingle.
Eric Schnapper argued the cause for respondents. With
h i m on the br ief were Ke i th L. Al tm an and Robe r t J.
Tolchin.*
Justice Thomas delivered the opinion of the Court.
Under 18 U. S. C. § 2333, United States nationals who have
been “injured . . . by reason of an act of international terror-
*Briefs of amici curiae urging reversal were fled for the Center for
Democracy & Technology et al. by Kathleen R. Hartnett, David D. Cole,
Aaron Mackey, Bruce D. Brown, Alex Abdo, Jennifer Stisa Granick, and
Patrick Toomey; for the Chamber of Commerce of the United States of
America et al. by Andrew J. Pincus and Paul Lettow; for the Computer &
Communications Industry Association et al. by Scott A. Keller and Steven
P. Lehotsky; for the Institute of International Bankers et al. by Marc J.
Gottridge, Lisa J. Fried, and Barron M. Flood; for InterAction et al. by
Timothy P. Harkness, Linda H. Martin, David Y. Livshiz, and Scott A.
Eisman; and for the Pharmaceutical Research and Manufacturers of
America by Beth S. Brinkman, David M. Zionts, Michael X. Imbroscio,
and S. Conrad Scott.
Briefs of amici curiae urging affrmance were fled for the American
Association of Jewish Lawyers and Jurists et al. by Hal R. Morris; for
the Anti-Defamation League by James P. Bonner, Patrick L. Rocco, and
Steven M. Freeman; for Anti-Terrorism Act Scholars by Stephen I. Vla-
deck, pro se; for Concerned Women for America by Mario Diaz, Gavriel
Mairone, and Adora Sauer; for Former National Security Offcials by
Gary M. Osen, Michael J. Radine, and Ari Ungar; for the Plaintiffs' Gen-
eral Committee by Carter G. Phillips, Jacqueline G. Cooper, Sean P. Car-
ter, Stephen A. Cozen, Richard D. Klingler, Jodi Westbrook, and John M.
Eubanks; for Retired United States Generals by Glenn A. Danas; and for
Sen. Charles E. Grassley by Michael A. Petrino.
Briefs of amici curiae were fled for Former State Department Legal
Advisers by Elbert Lin and Kevin S. Elliker; for 123 Victims of Terrorist
Attacks by Geoffrey P. Eaton and Tejinder Singh; and for 470 Victims of
Terrorist Attacks by Daniel Woofter and Erica Oleszczuk Evans.

478 TWITTER
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ism” may sue for damages. § 2333(a). They are not limited
to
suing the individual terrorists or organizations that di-
rectly carried out the attack, however. That is because
§ 2333(d)(2) also imposes civil liability on “any person who
aids and abets, by knowingly providing substantial assist-
ance, or who conspires with the person who committed such
an act of international terrorism.” Victims of terrorist acts
therefore may seek to recover from those who aided and
abetted the terrorist act that injured them.
The plaintiffs (who are respondents) contend that they
have stated a claim for relief under § 2333(d)(2). They were
allegedly injured by a terrorist attack carried out by ISIS.
But plai nti ffs are not sui ng ISIS. Instead, they have
brought suit against three of the largest social-media com-
panies in the world—Facebook, Twitter (who is petitioner),
and Google (which owns YouTube)—for allegedly aiding and
abetting ISIS. As plaintiffs allege, ISIS has used defend-
ants' social-media platforms to recruit new terrorists and to
raise funds for terrorism. Defendants allegedly knew that
ISIS was using their platforms but failed to stop it from
doing so. Plaintiffs accordingly seek to hold Facebook,
Twitter, and Google liable for the terrorist attack that alleg-
edly injured them. We conclude, however, that plaintiffs' al-
legations are insuffcient to establish that these defendants
aided and abetted ISIS in carrying out the relevant attack.
I
Plaintiffs' case arises from a 2017 terrorist attack on the
Reina nightclub in Istanbul, Turkey. The attack was car-
ried out by Abdulkadir Masharipov on behalf of the Islamic
State of Iraq and Syria (ISIS).
1
Born in Uzbekistan, Mash-
aripov had received military training with al Qaeda in Af-
ghanistan in 2011 and eventually became affliated with ISIS.
1
In one form or another, ISIS has been designated a Foreign Terrorist
Organization since 2004; it has also been known as the Islamic State of
Iraq and the Levant, al Qaeda in Iraq, and the al-Zarqawi Network.
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In 2016, he was ordered by ISIS to travel to Turkey and
launch
an attack in Istanbul on New Year's Eve. After
planning and coordinating the attack with ISIS emir Abu
Shuhada, Masharipov entered the Reina nightclub in the
early hours of January 1, 2017, and fred over 120 rounds into
a crowd of more than 700 people. In total, Masharipov
killed 39 people and injured 69 others. The next day, ISIS
released a statement claiming responsibility for the attack.
Two weeks later, Masharipov was arrested in Istanbul after
hiding out in ISIS safe houses.
One of Masharipov's victims was Nawras Alassaf, who was
killed in the attack. Several members of Alassaf 's family
then brought the present lawsuit under § 2333, alleging that
they had been injured by the attack.
2
Invoking § 2333(d)(2),
plaintiffs sued three major social-media companies—Face-
book, Inc., Google, Inc., and Twitter, Inc.—claiming that they
aided and abetted ISIS and thus were liable for the Reina
nightclub attack.
3
As is common knowledge, these three companies control
three of the largest and most ubiquitous platforms on the
internet: Facebook, YouTube, and Twitter. At the time of
the Reina attack, Facebook had over 2 billion active users
each month, YouTube had over 1 billion, and Twitter had
around 330 million. See Facebook, Inc., Form 10–K for Fis-
cal Year Ended Dec. 31, 2017, p. 34; Twitter, Inc., Form 10–
K for Fiscal Year Ended Dec. 31, 2017, p. 47; YouTube, You-
Tube Hits a Billion Monthly Users (Mar. 21, 2013), https://
blog.youtube/news-and-events/onebillionstrong. At least for
2
Plaintiffs appear to offer several theories as to the nature of their in-
jury; because that question is not before us, we take no position as to any
of those theories.
3
Although Twitter, Inc., is the named petitioner and defendant, Twitter,
Inc., has since been merged into X Corp., a subsidiary of X Holdings Corp.
Similarly, although Facebook, Inc., and Google, Inc., are the named defend-
ants, Facebook, Inc., is now known as Meta Platforms, Inc., and Google,
Inc., is now Google LLC, a subsidiary of Alphabet, Inc.
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Facebook and YouTube, those numbers are even higher
today
. See Meta Platforms, Inc., Form 10–K for Fiscal Year
Ended Dec. 31, 2022, p. 56 (nearly 3 billion); L. Ceci, Stat-
ista, YouTube–Statistics & Facts (Mar. 22, 2023), https://
www.statista.com/topics/2019/youtube/#topicOverview (2.56
billion).
Everyone before us today agrees on the basic aspects of
these platforms' business models. People from around the
world can sign up for the platforms and start posting content
on them, free of charge and without much (if any) advance
screening by defendants. Once on the platforms, users can
upload messages, videos, and other types of content, which
others on the platform can then view, respond to, and share.
As noted above, billions of people have done just that. As
a result, the amount of content on defendants' platforms is
staggering. It appears that for every minute of the day,
approximately 500 hours of video are uploaded to YouTube,
510,000 comments are posted on Facebook, and 347,000
tweets are sent on Twitter. See Statista, Media Usage in
an Internet Minute as of April 2022 (2023), https://www.
statista.com/statistics/195140/new-user-generated-content-
uploaded-by-users-per-minute; Statista, YouTube–Statis-
tics & Facts; B. Marr, How Much Data Do We Create Every
Day? Forbes, May 21, 2018. On YouTube alone, users col-
lectively watch more than 1 billion hours of video every day.
See YouTube Advertising, Reach Your Customers—and Dis-
cover New Ones, https://youtube.com/ intl/en_us/ads/how-it-
works/set-up-a-campaign/audience.
Defendants proft from this content largely by charging
third parties to advertise on their platforms. Those adver-
tisements are placed on or near the billions of videos, posts,
comments, and tweets uploaded by the platforms' users. To
organize and present all those advertisements and pieces of
content, defendants have developed “recommendation” algo-
rithms that automatically match advertisements and content
with each user; the algorithms generate those outputs based
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on a wide range of information about the user, the advertise-
ment,
and the content being viewed. So, for example, a per-
son who watches cooking shows on YouTube is more likely to
see cooking-based videos and advertisements for cookbooks,
whereas someone who likes to watch professorial lectures
might see collegiate debates and advertisements for TED
Talks.
But not all of the content on defendants' platforms is so
benign. As plaintiffs allege, ISIS and its adherents have
used these platforms for years as tools for recruiting, fund-
raising, and spreading their propaganda. Like many others
around the world, ISIS and its supporters opened accounts
on Facebook, YouTube, and Twitter and uploaded videos and
messages for others to see. Like most other content on
those platforms, ISIS' videos and messages were then
matched with other users based on those users' information
and use history. And, like most other content, advertise-
ments were displayed with ISIS' messages, posts, and videos
based on information about the viewer and the content being
viewed. Unlike most other content, however, ISIS' videos
and messages celebrated terrorism and recruited new terror-
ists. For example, ISIS uploaded videos that fundraised for
weapons of terror and that showed brutal executions of sol-
diers and civilians alike. And plaintiffs allege that these
platforms have been crucial to ISIS' growth, allowing it to
reach new audiences, gain new members, and spread its mes-
sage of terror.
Plaintiffs also allege that defendants have known that ISIS
has used their platforms for years. Yet, plaintiffs claim that
defendants have failed to detect and remove a substantial
number of ISIS-related accounts, posts, and videos. (For
example, plaintiffs aver that defendants “have failed to im-
plement . . . a basic account detection methodology” to pre-
vent ISIS supporters from generating multiple accounts on
their platforms. App. 150.) Accordingly, plaintiffs assert
that defendants aided and abetted ISIS by knowingly allow-

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ing ISIS and its supporters to use their platforms and beneft
from
their “recommendation” algorithms, enabling ISIS to
connect with the broader public, fundraise, and radicalize
new recruits. And, in the process, defendants allegedly
have profted from the advertisements placed on ISIS'
tweets, posts, and videos.
Plaintiffs also provide a set of allegations specifc to
Google. According to plaintiffs, Google has established a
system that shares revenue gained from certain advertise-
ments on YouTube w ith users who posted the v ideos
watched with the advertisement. As part of that system,
Google allegedly reviews and approves certain videos before
Google permits ads to accompany that video. Plaintiffs al-
lege that Google has reviewed and approved at least some
ISIS v ideos under that system, thereby shar i ng some
amount of revenue with ISIS.
The District Court dismissed plaintiffs' complaint for fail-
ure to state a claim.
4
But the Ninth Circuit reversed, fnd-
ing that plaintiffs had plausibly alleged that defendants aided
and abetted ISIS within the meaning of § 2333(d)(2) and thus
could be held secondarily liable for the Reina nightclub at-
tack. Gonzalez v. Google, 2 F. 4th 871 (2021). We granted
certiorari to resolve whether plaintiffs have adequately
stated such a claim under § 2333(d)(2). See 598 U. S. –––
(2022).
II
Section 2333 was originally enacted as part of the Antiter-
rorism Act (ATA) in 1990. 104 Stat. 2250. At that time,
Congress authorized United States nationals or their “estate,
survivors, or heirs” to bring civil lawsuits when “injured in
[their] person, property, or business by reason of an act of
4
Plaintiffs also raised other claims, including that defendants were di-
rectly liable for having provided material support to ISIS. See, e. g., 18
U. S. C. §§ 2333(a), 2339A, 2339B, 2339C. The District Court dismissed
those claims as well, and plaintiffs did not appeal them.

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international terrorism.” Id., at 2251.
5
In
such a lawsuit,
the plaintiff could recover treble damages and the cost of
the suit, including attorney's fees. See 18 U. S. C. § 2333(a).
But the ATA did not explicitly impose liability on anyone
who only helped the terrorists carry out the attack or con-
spired with them. Prior to 2016, some courts accordingly
determined that the ATA did not authorize that sort of sec-
ondary civil liability. See, e. g., Rothstein v. UBS AG, 708
F. 3d 82, 97–98 (CA2 2013).
Then, in 2016, Congress enacted the Justice Against Spon-
sors of Terrorism Act (JASTA) to provide for a form of sec-
ondary civil liability. 130 Stat. 852. Thus, as the law now
stands, those injured by an act of international terrorism can
sue the relevant terrorists directly under § 2333(a)—or they
can sue anyone “who aids and abets, by knowingly providing
substantial assistance, or who conspires with the person who
committed such an act of international terrorism” under
§ 2333(d)(2). For such a secondary-liability claim, there is an
5
The ATA defnes “international terrorism” to mean
“activities that—
“(A) involve violent acts or acts dangerous to human life that are a
violation of the criminal laws of the United States or of any State, or that
would be a criminal violation if committed within the jurisdiction of the
United States or of any State;
“(B) appear to be intended—
“(i) to intimidate or coerce a civilian population;
“(ii) to infuence the policy of a government by intimidation or coer-
cion; or
“(iii) to affect the conduct of a government by mass destruction, assassi-
nation, or kidnapping; and
“(C) occur primarily outside the territorial jurisdiction of the United
States, or transcend national boundaries in terms of the means by which
they are accomplished, the persons they appear intended to intimidate or
coerce, or the locale in which their perpetrators operate or seek asylum.”
§ 2331(1).
In short, the act generally must be violent, criminal, intended to in-
timidate or coerce civilians or a government, and occur either primarily
outside the United States or transcending national boundaries. See ibid.
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additional condition: The “act of international terrorism”
must
have been “committed, planned, or authorized by an
organization that had been designated as a foreign terrorist
organization under [8 U. S. C. § 1189] as of the date on which
such act of international terrorism was committed, planned,
or authorized.” Ibid. Plaintiffs seeking secondary liability
can likewise recover treble damages and the cost of the suit,
including attorney's fees. See §§ 2333(a), (d)(2).
The parties here do not dispute that the frst three compo-
nents of § 2333(d)(2) have been adequately alleged: The Reina
nightclub attack was an “act of international terrorism”; the
attack was “committed, planned, or authorized” by ISIS; and
ISIS was “designated as a foreign terrorist organization” as
of the date of the Reina nightclub attack. § 2333(d)(2). The
central question is thus whether defendants' conduct consti-
tutes “aid[ing] and abett[ing], by knowingly providing sub-
stantial assistance,” such that they can be held liable for the
Reina nightclub attack. Ibid.
III
As always, we start with the text of § 2333. See Barten-
werfer v. Buckley, 598 U. S. 69, 74 (2023). Here, that text
immediately begs two questions: First, what exactly does it
mean to “aid and abet”? Second, what precisely must the
defendant have “aided and abetted”?
A
We turn frst to the meaning of the phrase “aids and abets,
by knowingly providing substantial assistance.” Nothing in
the statute defnes any of those critical terms. Yet terms
like “aids and abets” are familiar to the common law, which
has long held aiders-and-abettors secondarily liable for the
wrongful acts of others. See Central Bank of Denver, N. A.
v. First Interstate Bank of Denver, N. A., 511 U. S. 164, 181
(1994). We generally presume that such common-law terms
“brin[g] the old soil” with them. Sekhar v. United States,
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570 U. S. 729, 733 (2013) (internal quotation marks omitted).
In
enacting JASTA, Congress provided additional context by
pointing to Halberstam v. Welch, 705 F. 2d 472 (CADC 1983),
as “provid[ing] the proper legal framework” for “civil aiding
and abetting and conspiracy liability.” § 2(a)(5), 130 Stat.
852.
6
We thus begin with Halberstam's “legal framework,”
viewed in context of the common-law tradition from which
it arose.
1
Long regarded as a leading case on civil aiding-and-abet-
ting and conspiracy liability, see 130 Stat. 852, Halberstam
arose from a distinctive fact pattern. Bernard Welch was a
serial burglar who had killed Michael Halberstam during a
break-in. 705 F. 2d, at 474. Halberstam's estate then sued
Welch's live-in partner, Linda Hamilton, for aiding and abet-
ting and conspiring with Welch. Id., at 474, 476.
7
Hamilton
was not present for Halberstam's murder, or even allegedly
aware of the murder. See id., at 474–476. But the facts
made clear that “[s]he was a willing partner in [Welch's]
criminal activities.” Id., at 474 (internal quotation marks
omitted). Hamilton had lived with Welch for fve years, dur-
ing which time the couple had risen from modest circum-
stances to possess a substantial fortune. Ibid. This rapid
ascent was remarkable because Welch had no outside em-
ployment. Id., at 475. Rather, he left the house most eve-
nings and returned with antiques, jewelry, and precious met-
6
The provision reads in full: “The decision of the United States Court
of Appeals for the District of Columbia in Halberstam v. Welch, 705 F. 2d
472 (D. C. Cir. 1983), which has been widely recognized as the leading
case regarding Federal civil aiding and abetting and conspiracy liability,
including by the Supreme Court of the United States, provides the proper
legal framework for how such liability should function in the context of
chapter 113B of title 18, United States Code.” § 2(a)(5), 130 Stat. 852.
7
Halberstam's estate also sued Welch himself; a default judgment was
entered against Welch, who did not appeal. See Halberstam, 705 F. 2d,
at 474.

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als—some of which he melted down into gold and silver
i
ngots by using a smelting furnace that he had installed in
their garage. Meanwhile, Hamilton did bookkeeping work
for Welch's “business,” facilitating the sale of those stolen
goods. Ibid. She had Welch's customers make checks pay-
able to her, falsifed her tax returns at Welch's direction, and
kept records of incoming payments from Welch's custom-
ers—with no records of outgoing funds to his “suppliers.”
Ibid. Their arrangement continued until Welch was ar-
rested after he killed Halberstam while burglarizing Halber-
stam's home. Ibid.
To determine Hamilton's liability, the D. C. Circuit under-
took an extensive survey of the common law, examining a
series of state and federal cases, the Restatement (Second)
of Torts, and prominent treatises that discussed secondary
liability in tort. Id., at 476–478, 481–486. With respect to
aiding and abetting, the court synthesized the cases as rest-
ing on three main elements: First, “the party whom the de-
fendant aids must perform a wrongful act that causes an
i n jury. ” Id., at 477. Second, “ the defendant must be
generally aware of his role as part of an overall illegal or
tortious activity at the time that he provides the assistance.”
Ibid. And, third, “the defendant must knowingly and sub-
stantially assist the principal violation.” Ibid. (citing, e. g.,
Landy v. Federal Deposit Ins. Corp., 486 F. 2d 139, 162–163
(CA3 1973); Woodward v. Metro Bank of Dallas, 522 F. 2d
84, 94–95 (CA5 1975)). Halberstam then articulated six fac-
tors to help determine whether a defendant's assistance was
“substantial.” 705 F. 2d, at 486–488. Those factors are (1)
“the nature of the act assisted,” (2) the “amount of assist-
ance” provided, (3) whether the defendant was “present at
the time” of the principal tort, (4) the defendant's “relation
to the tortious actor,” (5) the “defendant's state of mind,”
and (6) the “duration of the assistance” given. Id., at 488
(emphasis deleted). Last, Halberstam clarifed that those
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the act itself but also “for other reasonably foreseeable acts
done
in connection with it.” Id., at 484.
Applying that framework, the D. C. Circuit held that Ham-
ilton was liable for aiding and abetting Halberstam's murder.
Id., at 489.
8
The court frst determined that Welch had com-
mitted a wrong (in killing Halberstam during the burglary)
and that Hamilton was generally aware of her role in Welch's
criminal enterprise. Id., at 488. It then explained that
Hamilton had given knowing and substantial assistance to
Welch's activities by helping him turn his “stolen goods into
`legitimate' wealth,” thereby intending to help Welch suc-
ceed by performing a function crucial to any thief. Ibid.
And it clarifed that Hamilton knew Welch was commit-
ting some sort of “personal property crime,” the “foresee-
able risk” of which was “violence and killing.” Ibid. The
court therefore concluded that Hamilton substantially helped
Welch commit personal property crimes and was liable for
Halberstam's death, which was a foreseeable result of such
crimes. Ibid.
That articulation of the common law thus resolved Halber-
stam. But Halberstam recognized that the elements and
factors it provided could “be merged or articulated some-
what differently without affecting their basic thrust.” Id.,
at 478, n. 8. It thus cautioned—in a typical common-law
fashion—that its formulations should “not be accepted as im-
mutable components.” Id., at 489. Rather, Halberstam
suggested that its framework should be “adapted as new
cases test their usefulness in evaluating vicarious liability.”
Ibid.
2
The allegations before us today are a far cry from the facts
of Halberstam. Rather than dealing with a serial burglar
and his live-in partner-in-crime, we are faced with interna-
8
The D. C. Circuit also held that Hamilton was liable as a co-conspirator.
Id., at 489.
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tional terrorist networks and world-spanning internet plat-
f
or ms. By Halbe rstam's own l ights, its precise three-
element and six-factor test thus may not be entirely ade-
quate to resolve these new facts. Ibid. And JASTA itself
points only to Halberstam's “framework,” not its facts or its
exact phrasings and formulations, as the benchmark for aid-
ing and abetting. § 2(a)(5), 130 Stat. 852. We therefore
must ascertain the “basic thrust” of Halberstam's elements
and determine how to “adap[t]” its framework to the facts
before us today. See 705 F. 2d, at 478, 489, and n. 8. To do
so, we turn to the common law of aiding and abetting upon
which Halberstam rested and to which JASTA's common-law
terminology points.
As we have recognized, “[a]iding and abetting is an ancient
criminal law doctrine” that has substantially infuenced its
analog in tort. Central Bank of Denver, 511 U. S., at 181.
In one early statement of the criminal-law doctrine, William
Blackstone explained that those who were “present, aiding
and abetting the fact to be done,” or “procure[d], counsel[ed],
or command[ed] another to commit a crime,” were guilty and
punishable. 4 Commentaries on the Laws of England 34, 36
(1795). Over the years, many statutes and courts have of-
fered variations on that basic rule. See United States v.
Peoni, 100 F. 2d 401, 402 (CA2 1938) (L. Hand, J., for the
court) (collecting authorities). Yet, to this day, the basic
“view of culpability” that animates the doctrine is straight-
forward: “[A] person may be responsible for a crime he has
not personally carried out if he helps another to complete
its commission.” Rosemond v. United States, 572 U. S. 65,
70 (2014).
Importantly, the concept of “helping ” in the commission
of a crime—or a tort—has never been boundless. That is
because, if it were, aiding-and-abetting liability could sweep
in innocent bystanders as well as those who gave only tan-
gential assistance. For example, assume that any assistance
of any kind were suffcient to create liability. If that were
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the case, then anyone who passively watched a robbery could
be
said to commit aiding and abetting by failing to call the
police. Yet, our legal system generally does not impose lia-
bility for mere omissions, inactions, or nonfeasance; although
inaction can be culpable in the face of some independent duty
to act, the law does not impose a generalized duty to rescue.
See 1 W. LaFave, Substantive Criminal Law § 6.1 (3d ed.
2018) (LaFave); W. Keeton, D. Dobbs, R. Keeton, & D. Owen,
Prosser and Keeton on Law of Torts 373–375 (5th ed. 1984)
(Prosser & Keeton). Moreover, both criminal and tort law
typically sanction only “wrongful conduct,” bad acts, and
misfeasance. J. Goldberg, A. Sebok, & B. Zipursky, Tort
Law: Responsibilities and Redress 31 (2004). Some level of
blameworthiness is therefore ordinarily required. But,
again, if aiding-and-abetting liability were taken too far, then
ordinary merchants could become liable for any misuse of
their goods and services, no matter how attenuated their re-
lationship with the wrongdoer. And those who merely de-
liver mail or transmit emails could be liable for the tortious
messages contained therein. See Restatement (Second) of
Torts § 876, Comment d, Illus. 9, p. 318 (1979) (cautioning
against this result).
For these reasons, courts have long recognized the need to
cabin aiding-and-abetting liability to cases of truly culpable
conduct. They have cautioned, for example, that not “all
those present at the commission of a trespass are liable as
principals” merely because they “make no opposition or man-
ifest no disapprobation of the wrongful” acts of another.
Brown v. Perkins, 83 Mass. 89, 98 (1861); see also Hilmes v.
Stroebel, 59 Wis. 74, 17 N. W. 539 (1883); Duke v. Feldman,
245 Md. 454, 457–458, 226 A. 2d 345, 347 (1967). Put another
way, overly broad liability would allow for “one person [to]
be made a trespasser and even a felon against his or her
consent, and by the mere rashness or precipitancy or over-
heated zeal of another.” Bird v. Lynn, 49 Ky. 422, 423
(1850). Moreover, unlike its close cousin conspiracy, aiding

490 TWITTER
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and abetting does not require any agreement with the pri-
mary
wrongdoer to commit wrongful acts, thus eliminating
a signifcant limiting principle. See Nye & Nissen v. United
States, 336 U. S. 613, 620 (1949).
To keep aiding-and-abetting liability grounded in culpable
misconduct, criminal law thus requires “that a defendant `in
some sort associate himself with the venture, that he partici-
pate in it as in something that he wishes to bring about, that
he seek by his action to make it succeed' ” before he could
be held liable. Id., at 619 (quoting Peoni, 100 F. 2d, at 402).
In other words, the defendant has to take some “affrmative
act” “with the intent of facilitating the offense's commission.”
Rosemond, 572 U. S., at 71. Such intentional participation
can come in many forms, including abetting, inducing, en-
couraging, soliciting, or advising the commission of the of-
fense, such as through words of encouragement or driving
the getaway car. 2 LaFave § 13.2(a), at 457–460; see also
J. Hawley & M. McGregor, The Criminal Law 81 (3d ed.
1899). Regardless of the particulars, however, it is clear
that some culpable conduct is needed. See Rosemond, 572
U. S., at 73, 77.
9
Similar principles and concerns have shaped aiding-and-
abetting doctrine in tort law, with numerous cases directly
employing them to help articulate the standard for tortious
aiding and abetting. See, e. g., Zoelsch v. Arthur Ander-
sen & Co., 824 F. 2d 27, 35–36 (CADC 1987); Woodward, 522
F. 2d, at 95, n. 23; Landy, 486 F. 2d, at 163–164 (all relying
on Nye & Nissen, 336 U. S., at 619); see also Camp v. Dema,
948 F. 2d 455, 459 (CA8 1991) (relying on People v. Terman,
4 Cal. App. 2d 345, 346–347 (1935), another criminal case).
9
Conversely, conspiracy liability could be premised on a “more attenu-
ated relation with the principal violation” because the defendant and the
principal wrongdoer had agreed to a wrongful enterprise. Halberstam,
705 F. 2d, at 485; see also Restatement (Second) of Torts § 876, Comment
a, p. 316 (1979) (“The theory of the early common law was that there was
a mutual agency of each to act for the others”).
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Similar to the criminal-law rule, some cases have required
that
the defendant's assistance “must have had a direct rela-
tion to the trespass, and have been calculated and intended
to produce it” to warrant liability for the resulting tort.
Bird, 49 Ky., at 423; see also Smith v. Thompson, 103 Idaho
909, 911, 655 P. 2d 116, 118 (App. 1982); Brown, 83 Mass., at
98. Other cases have emphasized the need for some “culpa-
ble conduct” and “some degree of knowledge that [a defend-
ant's] actions are aiding the primary violator” before holding
the defendant secondarily liable. Camp, 948 F. 2d, at 460.
Still others have explained that “[c]ulpability of some sort is
necessary to justify punishment of a secondary actor,” lest
mostly passive actors like banks become liable for all of their
customers' crimes by virtue of carrying out routine transac-
tions. Monsen v. Consolidated Dressed Beef Co., 579 F. 2d
793, 799 (CA3 1978). And others have suggested that “inac-
tion cannot create liability as an aider and abettor” absent a
duty to act. Zoelsch, 824 F. 2d, at 36; see also Woodward,
522 F. 2d, at 96.
In articulating those limits, courts simultaneously began
to crystalize the framework for aiding and abetting that
Halberstam identifed and applied. See, e. g., Monsen, 579
F. 2d, at 799 (stating a similar three-part test).
10
As in
Halberstam, that framework generally required what the
text of § 2333(d)(2) demands: that the defendant have given
knowing and substantial assistance to the primary tortfea-
sor. See, e. g., Monsen, 579 F. 2d, at 799; Landy, 486 F. 2d,
at 162–163. Notably, courts often viewed those twin re-
quirements as working in tandem, with a lesser showing of
10
Others, however, have wondered whether any of these “elaborate dis-
cussions of the aiding and abetting standard . . . `have added anything
except unnecessary detail' ” to the formulation set forth by Judge Learned
Hand in United States v. Peoni, 100 F. 2d 401 (CA2 1938), and adopted by
this Court in Nye & Nissen v. United States, 336 U. S. 613 (1949). SEC
v. Apuzzo, 689 F. 3d 204, 212, n. 9 (CA2 2012) (quoting IIT, an Int'l Inv.
Trust v. Corn feld, 619 F. 2d 909, 922 (CA2 1980)).
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one demanding a greater showing of the other. E. g., Wood-
w
ard, 522 F. 2d, at 97; Woods v. Barnette Bank of Ft. Lau-
derdale, 765 F. 2d 1004, 1010 (CA11 1985). In other words,
less substantial assistance required more scienter before a
court could infer conscious and culpable assistance. See
Woodward, 522 F. 2d, at 97. And, vice versa, if the assist-
ance were direct and extraordinary, then a court might more
readily infer conscious participation in the underlying tort.
See ibid. In moving back and forth between all these guide-
posts, the courts thus largely tracked the same distinctions
drawn above to ensure that liability fell only on those who
had abetted the underlying tort through conscious, “culpable
conduct.” Camp, 948 F. 2d, at 460.
3
Halberstam's framework refected and distilled those
common-law principles. Indeed, Halberstam started with a
survey of many earlier common-law cases, including many of
the same cases cited above. 705 F. 2d, at 477, 483 (citing,
e. g., Woodward, 522 F. 2d, at 94–95; Landy, 486 F. 2d, at 162–
163; Duke, 245 Md., at 457–458, 226 A. 2d, at 347). As part
of that survey, Halberstam explicitly distinguished different
types of aid along the same culpability axis that grounded
the common law. 705 F. 2d, at 481– 483. For example,
Halberstam recognized that giving verbal encouragement
(such as yelling “ `Kill him!' ”) could be substantial assistance,
id., at 481, but that passively watching an assault after hear-
ing an assailant threaten the victim likely would not be, id.,
at 483. Those same lines have long been drawn for aiding-
and-abetting liability under the common law. See Rose-
mond, 572 U. S., at 70; see also, e. g., 2 LaFave § 13.2(a), at
457–460; Restatement (Second) of Torts § 876, Comment d,
Illus. 9–10, at 318; Brown, 83 Mass., at 98. And Halbers-
tam's six factors for “substantial assistance” call for the same
balancing that courts had undertaken previously between
the nature and amount of assistance on the one hand and
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the defendant's scienter on the other. 705 F. 2d, at 484–485,
487
–488.
Despite that deep-rooted common-law basis, the Ninth Cir-
cuit appears to have understood JASTA's approval of Halber-
stam's “legal framework” as requiring it to hew tightly to
the precise formulations that Halberstam used. The parties
before us similarly make a conscious effort to draw analogies
to the facts of that case. But any approach that too rigidly
focuses on Halberstam's facts or its exact phraseology risks
missi ng the mark. Ha lbe rstam is by its own ter ms a
common-law case and provided its elements and factors as a
way to synthesize the common-law approach to aiding and
abetting. And JASTA employs the common-law terms “aids
and abets,” pointing to Halberstam's common-law “frame-
work” as the primary guidepost for understanding the scope
of § 2333(d)(2).
At bottom, both JASTA and Halberstam's elements and
factors rest on the same conceptual core that has animated
aiding-and-abetting liability for centuries: that the defendant
consciously and culpably “participate[d]” in a wrongful act
so as to help “make it succeed.” Nye & Nissen, 336 U. S.,
at 619. To be sure, nuances may establish daylight between
the rules for aiding and abetting in criminal and tort law;
we have described the doctrines as “rough[ly] simila[r],” not
identical. Central Bank of Denver, 511 U. S., at 181. But
we need not resolve the extent of those differences today; it
is enough for our purposes to recognize the framework that
Halberstam set forth and the basis on which it rests. The
phrase “aids and abets” in § 2333(d)(2), as elsewhere, refers
to a conscious, voluntary, and culpable participation in anoth-
er's wrongdoing.
B
The next question, however, is what precisely a defendant
must aid and abet. As noted above, JASTA imposes liability
on anyone “who aids and abets, by knowingly providing
substantial assistance, or who conspires with the person
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who committed such an act of international terrorism.”
§
2333(d)(2). The parties vigorously dispute the textual ob-
ject of the term “aids and abets”: Plaintiffs assert that it
is “the person,” and defendants insist that it is the “act of
international terrorism.” So, plaintiffs contend, defendants
can be liable if they aided and abetted ISIS generally—there
is no need for defendants to have aided and abetted the spe-
cifc Reina nightclub attack. Conversely, defendants posit
that they are liable only if they directly aided and abetted
the Reina nightclub attack, with a strict nexus between their
assistance and that attack. Neither side is quite right.
To start, we fnd it unnecessary to parse whether the tex-
tual object of “aids and abets” is “the person” or the “act of
international terrorism.” That syntactic dispute makes lit-
tle difference here, because aiding and abetting is inherently
a rule of secondary liability for specifc wrongful acts. See
Prosser & Keeton 323. As stated above, the rule imposes
liability for a wrong on those who “hel[p] another to complete
i ts commission. ” Rosemond, 572 U. S., at 70 (emphasis
added). Or, as Halberstam put it, the defendant must aid
and abet “a tortious act.” 705 F. 2d, at 484.
Nor would a contrary rule make sense for torts. That is
because tort law imposes liability only when someone com-
mits an actual tort; merely agreeing to commit a tort or
suggesting a tortious act is not, without more, tortious. See
Prosser & Keeton 324; Halberstam, 705 F. 2d, at 479.
11
“Enterprises” or “conspiracies” alone are therefore not tor-
tious—the focus must remain on the tort itself. The same
11
In this respect, tort law is different from criminal law, which does
punish mere agreements to commit crimes. See, e. g., 2 LaFave § 12.2(b),
at 372 (“At common law a conspiracy was punishable even though no act
was done beyond the mere making of the agreement”); see also 1 J. Ohlin,
Wharton's Criminal Law § 8.7, p. 242 (16th ed. 2021) (noting that statutory
requirements of an “overt act” generally do not require that the overt act
be criminal); Iannelli v. United States, 420 U. S. 770, 785, n. 17 (1975)
(similar).
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is true here: The ATA opens the courthouse doors only if the
plai
ntiff is “injured . . . by reason of an act of international
terrorism.” § 2333(a). JASTA further restricts secondary
liability by requiring that the “act of international terror-
ism” be “committed, planned, or authorized by” a foreign ter-
rorist organization designated as such “as of the date on
which such act of international terrorism was committed,
planned, or authorized.” § 2333(d). Thus, it is not enough,
as plaintiffs contend, that a defendant have given substantial
assistance to a transcendent “enterprise” separate from and
foating above all the actionable wrongs that constitute it.
Rather, a defendant must have aided and abetted (by know-
ingly providing substantial assistance) another person in the
commission of the actionable wrong—here, an act of interna-
tional terrorism. See, e. g., Restatement (Second) of Torts
§ 876(b), and Comment d; Halberstam, 705 F. 2d, at 488.
Plaintiffs insist that Halberstam proves the contrary, but
their argument misses the gist of that case. To be sure,
Linda Hamilton was not on the scene for the burglary of
Halberstam's house and did not lend any specifc support to
Halberstam's murder. Ibid. But Hamilton's assistance to
Welch was so intentional and systematic that she assisted
each and every burglary committed by Welch; any time that
Welch left the house to burglarize, he would have relied on
Hamilton's assistance in laundering the stolen goods and
transforming them into usable wealth. See ibid. Thus,
Hamilton did aid and abet Welch in burglarizing Halbers-
tam's home—and, as noted above, killing Halberstam was a
foreseeable consequence of that burglary. See ibid.
On the other hand, defendants overstate the nexus that
§ 2333(d)(2) requires between the alleged assistance and the
wrongful act. To start, aiding and abetting does not require
the defendant to have known “all particulars of the primary
actor's plan.” Restatement (Third) of Torts: Intentional
Torts to Persons § 10, Comment c, p. 104 (Tent. Draft No. 3,
Apr. 6, 2018). For example, a defendant might be held liable

496 TWITTER
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for aiding and abetting the burning of a building if he inten-
ti
onally helped others break into the building at night and
then, unknown to him, the others lit torches to guide them
through the dark and accidentally started a fre. See Amer-
ican Family Mutual Ins. Co. v. Grim, 201 Kan. 340, 345–347,
440 P. 2d 621, 625–626 (1968); Restatement (Second) of Torts
§ 876, Comment d, Illus. 10, at 318. That leads to the next
problem: As Halberstam makes clear, people who aid and
abet a tort can be held liable for other torts that were “a
foreseeable risk” of the intended tort. 705 F. 2d, at 488.
Accordingly, a close nexus between the assistance and the
tort might help establish that the defendant aided and abet-
ted the tort, but even more remote support can still consti-
tute aiding and abetting in the right case.
Moreover, in appropriate circumstances, a secondary de-
fendant's role in an illicit enterprise can be so systemic that
the secondary defendant is aiding and abetting every wrong-
ful act committed by that enterprise—as in Halberstam it-
self. Id., at 487–488. At this point, aiding-and-abetting lia-
bility begins to blur with conspiracy liability, which typically
holds co-conspirators liable for all reasonably foreseeable
acts taken to further the conspiracy. See Pinkerton v.
United States, 328 U. S. 640, 647–648 (1946); see also Halber-
stam, 705 F. 2d, at 482–483 (noting the occasional overlap).
Yet, as noted above, aiding and abetting lacks the requisite
agreement that justifes such extensive conspiracy liability.
See Restatement (Second) of Torts § 876, Comment a, at 316
(“The theory of the early common law was that there was
mutual agency of each [conspirator] to act for the others”);
Pinkerton, 328 U. S., at 646. Thus, while the facts of Hal-
berstam are not totemic (lest courts strain to compare Linda
Hamilton with international criminal syndicates), its facts
are useful when determining whether a defendant has so
consciously “participate[d] in” a series of tortious acts in
order to “make [each one] succeed.” Nye & Nissen, 336
U. S., at 619 (internal quotation marks omitted).
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***
T
o summarize the requirements of § 2333(d)(2), the phrase
“aids and abets, by knowingly providing substantial as-
sistance,” points to the elements and factors articulated by
Halberstam. But, those elements and factors should not be
taken as infexible codes; rather, they should be understood
in light of the common law and applied as a framework de-
signed to hold defendants liable when they consciously and
culpably “participate[d] in” a tortious act in such a way as to
help “make it succeed.” Nye & Nissen, 336 U. S., at 619
(internal quotation marks omitted). And the text requires
that defendants have aided and abetted the act of interna-
tional terrorism that injured the plaintiffs—though that re-
quirement does not always demand a strict nexus between
the alleged assistance and the terrorist act.
IV
Under the appropriate framework, some aspects of today's
case become immediately clear: First, because they are try-
ing to hold defendants liable for the Reina attack, plaintiffs
must plausibly allege that defendants aided and abetted
ISIS
12
in carrying out that attack. Next, plaintiffs have sat-
isfed Halberstam's frst two elements by alleging both that
ISIS committed a wrong and that defendants knew they
were playing some sort of role in ISIS' enterprise. The key
question, therefore, is whether defendants gave such know-
ing and substantial assistance to ISIS that they culpably par-
ticipated in the Reina attack. The allegations here fall short
of that showing under Halberstam's framework as properly
12
For purposes of this case, we need not resolve whether defendants
must have aided and abetted ISIS, Masharipov, or some subgroup of ISIS
operatives in committing the Reina attack. In other words, we need not
resolve whether “the person” referred to in § 2333(d)(2) encompasses inter-
national terrorist syndicates or is somehow otherwise limited; either way,
defendants need to have aided and abetted that “person” in carrying out
the Reina attack.
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understood by reference to the common-law principles it
appl
ied.
A
To start, recall the basic ways that defendants as a group
allegedly helped ISIS. First, ISIS was active on defend-
ants' social-media platforms, which are generally available to
the internet-using public with little to no front-end screening
by defendants. In other words, ISIS was able to upload con-
tent to the platforms and connect with third parties, just like
everyone else. Second, defendants' recommendation algo-
rithms matched ISIS-related content to users most likely to
be interested in that content—again, just like any other con-
tent. And, third, defendants allegedly knew that ISIS was
uploading this content to such effect, but took insuffcient
steps to ensure that ISIS supporters and ISIS-related con-
tent were removed from their platforms. Notably, plaintiffs
never allege that ISIS used defendants' platforms to plan or
coordinate the Reina attack; in fact, they do not allege that
Masharipov himself ever used Facebook, YouTube, or Twitter.
None of those allegations suggest that defendants cul-
pably “associate[d themselves] with” the Reina attack, “par-
ticipate[d] in it as something that [they] wishe[d] to bring
about,” or sought “by [their] action to make it succeed.”
Nye & Nissen, 336 U. S., at 619 (internal quotation marks
ommitted). In part, that is because the only affrmative
“conduct” defendants allegedly undertook was creating their
platforms and setting up their algorithms to display content
relevant to user inputs and user history. Plaintiffs never
allege that, after defendants established their platforms,
they gave ISIS any special treatment or words of encourage-
ment. Nor is there reason to think that defendants selected
or took any action at all with respect to ISIS' content (ex-
cept, perhaps, blocking some of it).
13
Indeed, there is not
13
Plaintiffs concede that defendants attempted to remove at least some
ISIS-sponsored accounts and content after they were brought to their
attention.
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even reason to think that defendants carefully screened any
content
before allowing users to upload it onto their plat-
forms. If anything, the opposite is true: By plaintiffs' own
allegations, these platforms appear to transmit most content
without inspecting it.
The mere creation of those platforms, however, is not cul-
pable. To be sure, it might be that bad actors like ISIS are
able to use platforms like defendants' for illegal—and some-
times terrible—ends. But the same could be said of cell
phones, email, or the internet generally. Yet, we generally
do not think that internet or cell service providers incur cul-
pability merely for providing their services to the public writ
large. Nor do we think that such providers would normally
be described as aiding and abetting, for example, illegal drug
deals brokered over cell phones—even if the provider 's
conference-call or video-call features made the sale easier.
See Doe v. GTE Corp., 347 F. 3d 655, 659 (CA7 2003).
To be sure, plaintiffs assert that defendants' “recommen-
dation” algorithms go beyond passive aid and constitute ac-
tive, substantial assistance. We disagree. By plaintiffs'
own telling, their claim is based on defendants' “provision of
the infrastructure which provides material support to ISIS.”
App. 53. Viewed properly, defendants' “recommendation”
algorithms are merely part of that infrastructure. All the
content on their platforms is fltered through these algo-
rithms, which allegedly sort the content by information and
inputs provided by users and found in the content itself. As
presented here, the algorithms appear agnostic as to the na-
ture of the content, matching any content (including ISIS'
content) with any user who is more likely to view that con-
tent. The fact that these algorithms matched some ISIS
content with some users thus does not convert defendants'
passive assistance into active abetting. Once the platform
and sorting-tool algorithms were up and running, defendants
at most allegedly stood back and watched; they are not al-
leged to have taken any further action with respect to ISIS.
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At bottom, then, the claim here rests less on affrmative
misconduc
t and more on an alleged failure to stop ISIS from
using these platforms. But, as noted above, both tort and
criminal law have long been leery of imposing aiding-and-
abetting liability for mere passive nonfeasance. To show
that defendants' failure to stop ISIS from using these plat-
forms is somehow culpable with respect to the Reina attack,
a strong showing of assistance and scienter would thus be
required. Plaintiffs have not made that showing.
First, the relationship between defendants and the Reina
attack is highly attenuated. As noted above, defendants'
platforms are global in scale and allow hundreds of millions
(or billions) of people to upload vast quantities of information
on a daily basis. Yet, there are no allegations that defend-
ants treated ISIS any differently from anyone else. Rather,
defendants' relationship with ISIS and its supporters ap-
pears to have been the same as their relationship with their
billion-plus other users: arm's length, passive, and largely
indifferent. Cf. Halberstam, 705 F. 2d, at 488. And their
relationship with the Reina attack is even further removed,
given the lack of allegations connecting the Reina attack
with ISIS' use of these platforms.
Second, because of the distance between defendants' acts
(or failures to act) and the Reina attack, plaintiffs would need
some other very good reason to think that defendants were
consciously trying to help or otherwise “participate in” the
Reina attack. Nye & Nissen, 336 U. S., at 619 (internal quo-
tation marks omitted). But they have offered no such rea-
son, let alone a good one. Again, plaintiffs point to no act
of encouraging, soliciting, or advising the commission of
the Reina attack that would normally support an aiding-and-
abetting claim. See 2 LaFave § 13.2(a), at 457. Rather,
they essentially portray defendants as bystanders, watching
passively as ISIS carried out its nefarious schemes. Such
allegations do not state a claim for culpable assistance or
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participation in the Reina attack. See Halberstam, 705
F
. 2d, at 481, 483.
Because plaintiffs' complaint rests so heavily on defend-
ants' failure to act, their claims might have more purchase if
they could identify some independent duty in tort that would
have required defendants to remove ISIS' content. See
Woodward, 522 F. 2d, at 97, 100. But plaintiffs identify no
duty that would require defendants or other communication-
providing services to terminate customers after discovering
that the customers were using the service for illicit ends.
See Doe, 347 F. 3d, at 659; People v. Brophy, 49 Cal. App. 2d
15, 33–34 (1942).
14
To be sure, there may be situations
where some such duty exists, and we need not resolve the
issue today. Even if there were such a duty here, it would
not transform defendants' distant inaction into knowing and
substantial assistance that could establish aiding and abet-
ting the Reina attack.
If there were any doubt, the expansive scope of plaintiffs'
claims would put it to rest. Given the lack of any concrete
nexus between defendants' services and the Reina attack,
plaintiffs' claims would necessarily hold defendants liable as
having aided and abetted each and every ISIS terrorist act
committed anywhere in the world. Under plaintiffs' theory,
any U. S. national victimized by an ISIS attack could bring
the same claim based on the same services allegedly pro-
vided to ISIS. Plaintiffs thus must allege that defendants
so systemically and pervasively assisted ISIS that defend-
ants could be said to aid and abet every single ISIS attack.
14
Plaintiffs have not presented any case holding such a company liable
for merely failing to block such criminals despite knowing that they used
the company's services. Rather, when legislatures have wanted to impose
a duty to remove content on these types of entities, they have apparently
done so by statute. See, e. g., Telecommunications Act of 1996, § 502, 110
Stat. 133–134 (codifed, as amended, at 47 U. S. C. § 223); but see Reno v.
American Civil Liberties Union, 521 U. S. 844, 857, 874 (1997) (holding
parts of § 223 unconstitutional under the First Amendment).

502 TWITTER
, INC. v. TAAMNEH
Opinion of the Court
Viewed in that light, the allegations here certainly fall short.
Plai
ntiffs do not claim that defendants intentionally associ-
ated themselves with ISIS' operations or affrmatively gave
aid that would assist each of ISIS' terrorist acts. Nor have
they alleged that defendants and ISIS formed a near-
common enterprise of the kind that could establish such
broad liability. These allegations are thus a far cry from the
type of pervasive, systemic, and culpable assistance to a se-
ries of terrorist activities that could be described as aiding
and abetting each terrorist act.
To be sure, we cannot rule out the possibility that some
set of allegations involving aid to a known terrorist group
would justify holding a secondary defendant liable for all of
the group's actions or perhaps some defnable subset of ter-
rorist acts. There may be, for example, situations where
the provider of routine services does so in an unusual way
or provides such dangerous wares that selling those goods
to a terrorist group could constitute aiding and abetting a
foreseeable terror attack. Cf. Direct Sales Co. v. United
States, 319 U. S. 703, 707, 711–712, 714–715 (1943) (registered
morphine distributor could be liable as a co-conspirator of an
illicit operation to which it mailed morphine far in excess of
normal amounts). Or, if a platform consciously and selec-
tively chose to promote content provided by a particular ter-
rorist group, perhaps it could be said to have culpably as-
sisted the terrorist group. Cf. Passaic Daily News v. Blair,
63 N. J. 474, 487–488, 308 A. 2d 649, 656 (1973) (publishing
employment advertisements that discriminate on the basis
of sex could aid and abet the discrimination).
In those cases, the defendants would arguably have of-
fered aid that is more direct, active, and substantial than
what we review here; in such cases, plaintiffs might be able
to establish liability with a lesser showing of scienter. But
we need not consider every iteration on this theme. In this
case, it is enough that there is no allegation that the plat-
forms here do more than transmit information by billions of
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people, most of whom use the platforms for interactions that
once
took place via mail, on the phone, or in public areas.
The fact that some bad actors took advantage of these plat-
forms is insuffcient to state a claim that defendants know-
ingly gave substantial assistance and thereby aided and abet-
ted those wrongdoers' acts. And that is particularly true
because a contrary holding would effectively hold any sort of
communication provider liable for any sort of wrongdoing
merely for knowing that the wrongdoers were using its serv-
ices and failing to stop them. That conclusion would run
roughshod over the typical limits on tort liability and take
aiding and abetting far beyond its essential culpability
moorings.
B
In holding that plaintiffs had stated a claim, the Ninth Cir-
cuit went astray through a series of missteps that, together,
obscured the essence of aiding-and-abetting liability. To
correct those errors, we proceed through the Ninth Circuit's
application of Halberstam's framework.
The Ninth Circuit framed the issue of substantial assist-
ance as turning on defendants' assistance to ISIS' activities
in general. See 2 F. 4th, at 909. But, as we explained
above, the question is whether defendants gave substantial
assistance to ISIS with respect to the Reina attack. The
focus thus must remain on the Reina attack; plaintiffs' failure
to allege any defnable nexus between the defendants' assist-
ance and that attack therefore—at minimum—drastically in-
creases their burden to show that defendants somehow con-
sciously and culpably assisted the attack.
Next, the Ninth Circuit misapplied the “knowing ” half of
“knowing and substantial assistance.” It frst separated the
“knowing ” and “substantial” subelements; it then analyzed
the “knowing ” subelement as a carbon copy of the ante-
cedent element of whether the defendants were “generally
aware” of their role in ISIS' overall scheme. Ibid.; see also
id., at 908. But, as discussed above, “the knowledge and
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substantial assistance” components “should be considered
relative
to one another” as part of a single inquiry designed
to capture conscious and culpable conduct. Camp, 948 F. 2d,
at 459 (internal quotation marks omitted). The “knowing ”
part of that inquiry is therefore designed to capture the de-
fendants' state of mind with respect to their actions and the
tortious conduct (even if not always the particular terrorist
act), not the same general awareness that defnes Halber-
stam's second element.
Finally, when applying Halberstam's six substantiality fac-
tors, the Ninth Circuit appears to have regarded the factors
as a sequence of disparate, unrelated considerations without
a common conceptual core. See 2 F. 4th, at 909–910. That
is incorrect. The point of those factors is to help courts cap-
ture the essence of aiding and abetting: participation in
another's wrongdoing that is both signifcant and culpable
enough to justify attributing the principal wrongdoing to the
aider and abettor. The Ninth Circuit thus erred in focusing
(as it did) primarily on the value of defendants' platforms
to ISIS, rather than whether defendants culpably associated
themselves with ISIS' actions. For example, when applying
the second factor (the amount and kind of assistance), the
Ninth Circuit should have considered that defendants' plat-
forms and content-sorting algorithms were generally avail-
able to the internet-using public. That focus reveals that
ISIS' ability to beneft from these platforms was merely inci-
dental to defendants' services and general business models;
it was not attributable to any culpable conduct of defendants
directed toward ISIS. And, when considering the fourth
and ffth factors (the defendants' relationship to ISIS and the
defendants' state of mind), the Ninth Circuit should have
given much greater weight to defendants' arm's-length rela-
tionship with ISIS—which was essentially no different from
their relationship with their millions or billions of other
users—and their undisputed lack of intent to support ISIS.
See id., at 910.
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Taken as a whole, the Ninth Circuit's analytic approach
thus
elided the fundamental question of aiding-and-abetting
liability: Did defendants consciously, voluntarily, and culpa-
bly participate in or support the relevant wrongdoing? As
we have explained above, the answer in this case is no.
Plaintiffs allege only that defendants supplied generally
available virtual platforms that ISIS made use of, and that
defendants failed to stop ISIS despite knowing it was using
those platforms. Given the lack of nexus between that as-
sistance and the Reina attack, the lack of any defendant in-
tending to assist ISIS, and the lack of any sort of affrmative
and culpable misconduct that would aid ISIS, plaintiffs'
claims fall far short of plausibly alleging that defendants
aided and abetted the Reina attack.
C
That leaves the set of allegations specifc to Google. As
explained above, plaintiffs allege that Google reviewed and
approved ISIS videos on YouTube as part of its revenue-
sharing system and thereby shared advertising revenue with
ISIS. The Ninth Circuit briefy mentioned those allegations
when analyzing plaintiffs' complaint here. However, in ad-
dressing another, materially identical complaint, the Ninth
Circuit held that the same allegations “failed to state a claim
for aiding-and-abetting liability” because they were “devoid
of any allegations about how much assistance Google pro-
vided” and therefore did not plausibly allege “that Google's
assistance was substantial.” Id., at 907.
We think that the Ninth Circuit was correct in that hold-
ing. The complaint here alleges nothing about the amount
of money that Google supposedly shared with ISIS, the num-
ber of accounts approved for revenue sharing, or the content
of the videos that were approved. It thus could be the case
that Google approved only one ISIS-related video and shared
only $50 with someone affliated with ISIS; the complaint
simply does not say, nor does it give any other reason to view
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Google's revenue sharing as substantial assistance. Without
more
, plaintiffs thus have not plausibly alleged that Google
knowingly provided substantial assistance to the Reina at-
tack, let alone (as their theory of liability requires) every
single terrorist act committed by ISIS.
V
By their very nature, the concepts of aiding and abetting
and substantial assistance do not lend themselves to crisp,
bright-line distinctions. However, both the common law and
Halberstam provide some clear guideposts: The point of aid-
ing and abetting is to impose liability on those who con-
sciously and culpably participated in the tort at issue. The
focus must remain on assistance to the tort for which plain-
tiffs seek to impose liability. When there is a direct nexus
between the defendant's acts and the tort, courts may more
easily infer such culpable assistance. But, the more attenu-
ated the nexus, the more courts should demand that plain-
tiffs show culpable participation through intentional aid that
substantially furthered the tort. And, if a plaintiff 's theory
would hold a defendant liable for all the torts of an enter-
prise, then a showing of pervasive and systemic aid is re-
quired to ensure that defendants actually aided and abetted
each tort of that enterprise.
Here, however, the nexus between defendants and the
Reina attack is far removed. As alleged by plaintiffs, de-
fendants designed virtual platforms and knowingly failed to
do “enough” to remove ISIS-affliated users and ISIS-related
content—out of hundreds of millions of users worldwide and
an immense ocean of content—from their platforms. Yet,
plaintiffs have failed to allege that defendants intentionally
provided any substantial aid to the Reina attack or other-
wise consciously participated in the Reina attack—much less
that defendants so pervasively and systemically assisted
ISIS as to render them liable for every ISIS attack. Plain-
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Jackson, J., concurring
ti ffs accordi ng ly have fai led to st ate a clai m under
§
2333(d)(2).
We therefore reverse the judgment of the Ninth Circuit.
It is so ordered.
Justice Jackson, concurring.
I join the opinion of the Court with the understanding that
today's decisions are narrow in important respects. In this
case and its companion, Gonzalez v. Google, 598 U. S. 617
(2023) (per curiam), the Court has applied 18 U. S. C.
§ 2333(d)(2) to two closely related complaints, fled by the
same counsel. Both cases came to this Court at the motion-
to-dismiss stage, with no factual record. And the Court's
view of the facts—including its characterizations of the
social-media platforms and algorithms at issue—properly
rests on the particular allegations in those complaints.
Other cases presenting different allegations and different
records may lead to different conclusions.
The Court also draws on general principles of tort and
criminal law to inform its understanding of § 2333(d)(2).
General principles are not, however, universal. The
common-law propositions this Court identifes in interpret-
ing § 2333(d)(2) do not necessarily translate to other contexts.
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Reporter’s Note
The attached opinion has been revised to refect the usual publication
and citation style of the United States Reports. The revised pagination
makes available the offcial United States Reports citation in advance of
publication. The syllabus has been prepared by the Reporter of Decisions
for the convenience of the reader and constitutes no part of the opinion of
the Court. A list of counsel who argued or fled briefs in this case, and
who were members of the bar of this Court at the time this case was
argued, has been inserted following the syllabus. Other revisions may
include adjustments to formatting, captions, citation form, and any errant
punctuation. The following additional edits were made:
None