Oklahoma v. EPA

P R E L I M I N A R Y P R I N T
Volume 605 U. S. Part 2
Pages 609–626
OFFICIAL REPORTS
OF
T H E S U P R E M E C O U R T
June 18, 2025
REBECCA A. WOMELDORF
reporter of decisions
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609
Syllabus
OKLAHOMA et al. v. ENVIRONMENTAL
PROTECTION
AGENCY et al.
certiorari to the united states court of appeals for
the tenth circuit
No. 23–1067. Argued March 25, 2025—Decided June 18, 2025*
The Clean Air Act (CAA) channels challenges to Environmental Protec-
tion Agency (EPA) actions to the U. S. Court of Appeals for the D. C.
Circuit if the actions are “nationally applicable,” and to a regional
Circuit if they are “locally or regionally applicable.” 42 U. S. C.
§ 7607(b)(1). The CAA contains an exception for certain “locally or re-
gionally applicable” actions “based on a determination of nationwide
scope or effect,” which also must be brought in the D. C. Circuit. Ibid.
In 2015, EPA revised the national ambient air quality standards
(NAAQS) for ozone to be more stringent. Each State submitted a state
implementation plan (SIP) detailing how it would comply with the
CAA's “Good Neighbor” provision, which requires SIPs to “contain ade-
quate provisions” “prohibiting ” in-state emissions activity that would
interfere with other States' NAAQS compliance. § 7410(a)(2)(D)(i)(I).
EPA ultimately disapproved 21 States' SIPs for failure to comply with
the Good Neighbor provision. These States had asserted they did not
need to propose new emissions-reduction measures, but EPA disagreed
after considering the “contents of each individual state's submission”
“on its own merits” and making individual determinations for each SIP.
88 Fed. Reg. 9354.
EPA aggregated its disapprovals into one omnibus Federal Register
rule describing EPA's “4-step framework” for evaluating SIP submis-
sions. EPA asserted in the rule that its disapprovals would be review-
able only in the D. C. Circuit as either nationally applicable actions or,
alternatively, as locally or regionally applicable actions falling within
the “nationwide scope or effect” exception based on EPA's use of “the
same, nationally consistent 4-step . . . framework” and its evaluation for
“national consistency.” Id., at 9380–9381.
States and industry petitioners challenged EPA's SIP disapprovals in
regional Circuits. Of fve Circuits to resolve EPA's motions to dismiss
or transfer, four found regional Circuit review proper. Only the Tenth
Circuit disagreed, granting EPA's motion to transfer suits by Oklahoma
*Together with No. 23–1068, PacifCorp et al. v. Environmental Protec-
tion Agency et al., also on certiorari to the same court.

610 OKLAH
OMA v. EPA
Syllabus
and Utah. The Tenth Circuit concluded that EPA's omnibus rule consti-
tuted
a single, nationally applicable action because it covered “21 states
across the country” and refected EPA's application of “a uniform statu-
tory interpretation and common analytical methods.” 93 F. 4th 1262,
1266.
Held: EPA's disapprovals of the Oklahoma and Utah SIPs are locally or re-
gionally applicable actions reviewable in a regional Circuit. Pp. 618–625.
(a) Applying the framework from EPA v. Calumet Shreveport Refn-
ing, L.L.C., 605 U. S. 627, venue determination under § 7607(b)(1) re-
quires a two-step inquiry. First, courts identify the relevant EPA “ac-
tion” and ask whether it is “nationally applicable” or only “locally or
regionally applicable.” If nationally applicable, challenges belong in
the D. C. Circuit. If locally or regionally applicable, courts proceed to
the second step to determine whether the “nationwide scope or effect”
exception applies to override the default rule of regional Circuit review.
An “action” under § 7607(b)(1) is a “particular exercis[e] of EPA au-
thority undertaken pursuant to [a] particular CAA provisio[n].” Id., at
637. Courts determine the relevant “action” by reference to the CAA
provision under which EPA acted, not how EPA presented its decision.
Each EPA SIP approval constitutes its own “action.” Section
7607(b)(1) enumerates an individual SIP approval as an example of a
locally or regionally applicable action, referring expressly to EPA's “ac-
tion in approving . . . any implementation plan under section 7410.” It
follows that each EPA SIP disapproval is also its own action, since EPA
undertakes SIP disapprovals pursuant to the same CAA authority un-
derlying SIP approvals. Section 7410 directs each State to adopt and
submit a plan for NAAQS implementation and directs EPA to either
approve or disapprove it. Thus, EPA's approvals and disapprovals are
opposite sides of the same coin.
The two SIP disapprovals here are undisputedly locally or regionally
applicable actions. A SIP is a state-specifc plan, so an EPA disap-
proval on its face applies only to the State that proposed the SIP. An
EPA decision on an individual SIP “is the prototypical `locally or region-
ally applicable' action.” American Road & Transp. Builders Assn. v.
EPA, 705 F. 3d 453, 455. Pp. 618–620.
(b) EPA's and the Tenth Circuit's contrary arguments fail. Section
7607(b)(1) “makes the CAA's framing of the relevant `action' controlling,
regardless of how EPA chooses to package its decisions in the Federal
Register.” Calumet, 605 U. S., at 638. Although EPA was free to ag-
gregate its SIP disapprovals into one rule, that aggregation has no sig-
nifcance for venue purposes. The Tenth Circuit's view that EPA's “ac-
tion” is whatever it has “chosen to issue,” 93 F. 4th, at 1267, fails to
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as: 605 U. S. 609 (2025)
611
Syllabus
grapple with what § 7607(b)(1) means by “action,” which is defned by
reference
to the underlying CAA provision, not EPA's stylization, Calu-
met, 605 U. S., at 637.
The Tenth Circuit also erred in deeming EPA's actions nationally ap-
plicable based on EPA's use of “uniform statutory interpretation and
common analytical methods.” 93 F. 4th, at 1266. The “applicability”
of an action turns on its formal geographical scope. An action “applies”
nationally only if, on its face, it has binding effect throughout the coun-
try. Calumet, 605 U. S., at 638–639. EPA's interpretive and analytical
methodology goes to its underlying reasoning, which matters only at
the second § 7607(b)(1) step. Pp. 621–622.
(c) Because EPA's SIP disapprovals are locally or regionally applica-
ble, the Court must determine whether the “nationwide scope or effect”
exception applies. This exception requires that (1) the action “is based
on a determination of nationwide scope or effect,” and (2) EPA “fnds
and publishes that such action is based on such a determination.”
§ 7607(b)(1). The second requirement is satisfed because EPA included
an express fnding in its Federal Register notice. The Court holds that
EPA's SIP disapprovals were not based on any determination of nation-
wide scope or effect.
This requirement is met only if “a justifcation of nationwide breadth
is the primary explanation for and driver of EPA's action.” Calumet,
605 U. S., at 645. Such a justifcation “does not rise to this level if EPA
also relied in signifcant part on other, `intensely factual' considerations,
or if the key driver of EPA's action is otherwise debatable.” Ibid.
EPA's disapprovals fall into the latter category.
EPA's omnibus rule makes clear that its SIP disapprovals were based
on “a number of intensely factual determinations” particular to each
State. Texas v. EPA, 829 F. 3d 405, 421. EPA evaluated the contents
of each SIP “on their own merits,” considering state-specifc facts and
information available to each State. 88 Fed. Reg. 9354. From this
state-specifc analysis, EPA produced for each State a unique list of
“bases for disapproval.” Ibid. For Oklahoma, EPA rejected its at-
tempt to disclaim responsibility for certain emissions in Texas and
faulted it for “insuffcient evaluation of additional emissions control op-
portunities.” Id., at 9359. For Utah, EPA found inadequate justifca-
tion for Utah's attempt to discount certain emissions in Colorado, as
well as “technical and legal faws in the State's arguments” regarding
various emissions considerations. Id., at 9360.
This state-specifc analysis contrasts sharply with EPA's justifcations
in Calumet, where EPA made determinations that applied uniformly to
all small refneries and used them to reach a presumptive conclusion,
considering refnery-specifc facts only to confrm that there is no reason
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612 OKLAH
OMA v. EPA
Syllabus
to depart from the presumptive disposition. Here, no nationwide factor
settles
EPA's ultimate decisions. Instead, EPA disapproved Oklaho-
ma's and Utah's SIPs after conducting predominantly fact-intensive,
state-specifc analysis.
The four determinations EPA proffers—use of updated 2016-based
modeling, application of a 1% contribution threshold, determination that
other States' contributions could not excuse analyzing whether their
own emissions signifcantly contribute downwind, and its position that
States cannot rely on emission-reduction measures not incorporated into
state plans—qualify as determinations of nationwide scope or effect.
But these conclusions are at most heuristics that aided EPA's analysis
rather than primary drivers of the disapprovals. None makes clear
why EPA concluded that Oklahoma and Utah had produced inadequate
proposals for Good Neighbor compliance. For example, EPA's 1% con-
tribution threshold was used only for “screening ” purposes to determine
when further evaluation was needed, but “there was still a lot of work
to be done” before EPA could issue disapprovals. Tr. of Oral Arg. 38.
Pp. 622–625.
93 F. 4th 1262, reversed and remanded.
Thomas, J., delivered the opinion of the Court, in which Sotomayor,
Kagan, Kavanaugh, Barrett, and Jackson, JJ., joined. Gorsuch, J.,
fled an opinion concurring in the judgment, in which Roberts, C. J.,
joined, post, p. 626. Alito, J., took no part in the consideration or decision
of the cases.
Mithun Mansinghani argued the cause for petitioners in
No. 23–1067. With him on the briefs were Gentner Drum-
mond, Attorney General of Oklahoma, Garry M. Gaskins II,
Solicitor General, Jennifer L. Lewis, Deputy Attorney Gen-
eral, Sean D. Reyes, former Attorney General of Utah, Derek
Brown, Attorney General, Stanford E. Purser, Solicitor Gen-
eral, William L. Wehrum, Emily C. Schilling, Kristina R.
Van Bockern, Michael B. Schon, and Drew F. Waldbeser.
Misha Tseytlin argued the cause for petitioners in No. 23–
1068. With him on the briefs were Jeff P. Johnson, Kevin
M. LeRoy, Megan Berge, Aaron M. Streett, J. Mark Little,
David C. Reymann, Marie Bradshaw Durrant, Christian C.
Stephens, Carroll Wade McGuffey III, Artemis D. Vamia-
nakis, Alan I. Robbins, and Debra D. Roby.

Cite
as: 605 U. S. 609 (2025)
613
Counsel
Deputy Solicitor General Stewart argued the cause for re-
spondents
in both cases. With him on the brief were Solici-
tor General Prelogar, Acting Assistant Attorney General
Konschnik, Aimee W. Brown, Alexandra L. St. Romain, Su-
sannah Weaver, Matthew Marks, Rosemary H. Kaban, and
Emily Seidman.†
†A brief of amici curiae urging reversal in both cases was fled for the
State of Arkansas et al. by Tim Griffn, Attorney General of Arkansas,
Nicholas J. Bronni, Solicitor General, Dylan L. Jacobs, Deputy Solicitor
General, and Asher L. Steinberg, Senior Assistant Solicitor General, and
by the Attorneys General for their respective States as follows: Steve Mar-
shall of Alabama, Treg Taylor of Alaska, Ashley Moody of Florida, Chris-
topher Carr of Georgia, Raúl Labrador of Idaho, Theodore E. Rokita of
Indiana, Brenna Bird of Iowa, Kris W. Kobach of Kansas, Liz Murrill of
Louisiana, Lynn Fitch of Mississippi, Andrew Bailey of Missouri, Austin
Knudsen of Montana, Michael T. Hilgers of Nebraska, Drew H. Wrigley
of North Dakota, Dave Yost of Ohio, Alan Wilson of South Carolina,
Marty Jackley of South Dakota, Jonathan Skrmetti of Tennessee, Ken
Paxton of Texas, Jason S. Miyares of Virginia, Patrick Morrisey of West
Virginia, and Bridget Hill of Wyoming. Jennifer L. Mascott and R. Trent
McCotter fled a brief for Sen. Mike Lee et al. as amici curiae urging
reversal in No. 23–1067.
Briefs of amici curiae urging affrmance in both cases were fled for the
State of New York et al. by Letitia James, Attorney General of New York,
Barbara D. Underwood, Solicitor General, Judith N. Vale, Deputy Solicitor
General, Elizabeth A. Brody, Assistant Solicitor General, and Morgan A.
Costello and Claiborne E. Walthall, Assistant Attorneys General, by
Christian Menefee, and by the Attorneys General for their respective ju-
risdictions as follows: Kris Mayes of Arizona, William Tong of Connecti-
cut, Kathleen Jennings of Delaware, Brian L. Schwalb of the District of
Columbia, Anne E. Lopez of Hawaii, Kwame Raoul of Illinois, Aaron M.
Frey of Maine, Anthony G. Brown of Maryland, Andrea Joy Campbell of
Massachusetts, Dana Nessel of Michigan, Matthew J. Platkin of New Jer-
sey, Raúl Torrez of New Mexico, Dan Rayfeld of Oregon, Peter F. Ner-
onha of Rhode Island, Charity R. Clark of Vermont, Nicholas W. Brown
of Washington, and Joshua L. Kaul of Wisconsin; and for Jonathan Cannon
et al. by Matthew J. Sanders and Deborah A. Sivas.
Jeremy C. Marwell, Jennifer B. Dickey, Andrew R. Varcoe, and Eric
Groten fled a brief for the Chamber of Commerce of the United States of
America as amicus curiae in both cases.
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614 OKLAH
OMA v. EPA
Opinion of the Court
Justice Thomas delivered the opinion of the Court.
P
etitioners seek judicial review of the Environmental Pro-
tection Agency's (EPA's) disapprovals of two state emissions-
control plans. These cases require us to decide the proper
venue for their challenges. The Clean Air Act (CAA) chan-
nels these challenges to the U. S. Court of Appeals for the
D. C. Circuit if EPA's disapprovals are “nationally applica-
ble,” and to a regional Circuit if they are “locally or region-
ally applicable.” 42 U. S. C. § 7607(b)(1). But, the CAA
contains an exception for certain “locally or regionally appli-
cable” actions “based on a determination of nationwide scope
or effect,” which also must be brought in the D. C. Circuit.
Ibid. Applying the interpretation of § 7607(b)(1) that we
outlined today in EPA v. Calumet Shreveport Refning,
L.L.C., 605 U. S. 627 (2025), we hold that EPA's disapprovals
are locally or regionally applicable actions reviewable in a
regional Circuit.
I
A
The CAA's venue provision, § 7607(b)(1), dictates where
petitioners should challenge EPA actions taken under that
statute. This provision enumerates certain “nationally ap-
plicable” actions that must be brought in the D. C. Circuit,
and certain “locally or regionally applicable” actions that
must be brought in a regional Circuit. § 7607(b)(1). It then
provides catchall clauses requiring the same treatment of all
other “nationally applicable” and “locally or regionally appli-
cable” actions. Ibid. But, § 7607(b)(1) includes one excep-
tion to its default rule for locally or regionally applicable
actions: A challenge to such an action belongs in the D. C.
Circuit if (1) it “is based on a determination of nationwide
scope or effect,” and (2) “in taking such action [EPA] fnds
and publishes that such action is based on such a determina-
tion.” Ibid.
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as: 605 U. S. 609 (2025)
615
Opinion of the Court
In Calumet, we explained that determining venue under
§
7607(b)(1) requires a two-step inquiry. 605 U. S., at 636.
At the frst step, we identify the relevant EPA “action” and
ask whether it is “nationally applicable” or only “locally or
regionally applicable.” § 7607(b)(1). If the action is “na-
tionally applicable,” then any challenge to it belongs in the
D. C. Circuit. Ibid. But, if the action is “locally or region-
ally applicable,” then we proceed to the second step, where
we ask whether the “nationwide scope or effect” exception
applies to override § 7607(b)(1)'s default rule that “locally or
regionally applicable” actions are reviewable only in the re-
gional Circuits. Ibid. If the exception applies, then any
challenge to the action must be brought in the D. C. Cir-
cuit. Ibid.
B
These cases arise from EPA's review of “State implemen-
tation plans” (SIPs)—i. e., state proposals for how to comply
with an EPA “national primary or secondary ambient air
quality standard” (NAAQS). See § 7410. The CAA makes
the SIP process one of federal-state collaboration. EPA
frst sets a NAAQS, which “represents `the maximum air-
borne concentration of [a] pollutant that the public health can
tolerate.' ” West Virginia v. EPA, 597 U. S. 697, 707 (2022);
see § 7409(b). But, States bear “primary responsibility” for
deciding how a NAAQS should be attained. § 7401(a)(3).
States must propose SIPs that “provid[e] for [the] implemen-
tation, maintenance, and enforcement” of a NAAQS within
their jurisdictions. § 7410(a)(1). EPA then approves or dis-
approves each SIP based on whether it meets the “applicable
requirements” of the CAA. § 7410(k)(3). If EPA disap-
proves a SIP, then EPA must issue a “[f]ederal implementa-
tion plan” for that State within two years. § 7410(c)(1). A
State can avoid this outcome only if it “corrects the def-
ciency” and gains EPA approval for its revised SIP before
EPA promulgates the federal plan. Ibid.
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616 OKLAH
OMA v. EPA
Opinion of the Court
In 2015, EPA triggered the SIP process by revising the
N
AAQS for ozone to be more stringent. 80 Fed. Reg. 65294.
Each State in turn submitted a SIP, which, as relevant here,
detailed how the submitting State would comply with the
CA A's “Good Neighbor ” provisi on, § 7410(a)(2)(D)( i)(I).
That provision accounts for the “externality” that “[b]ecause
air currents can carry pollution across state borders, emis-
sions in upwind States sometimes affect air quality in down-
wind States.” Ohio v. EPA, 603 U. S. 279, 283–284 (2024).
In particular, the provision requires SIPs to “contain ade-
quate provisions . . . prohibiting ” in-state “emissions activ-
ity” that would interfere with other States' NAAQS compli-
ance. § 7410(a)(2)(D)(i)(I).
EPA ultimately disapproved 21 States' SIPs for failure to
comply with the “Good Neighbor” provision. 88 Fed. Reg.
9336 (2023). These States had all asserted in their SIPs that
they did not need to propose new emissions-reduction meas-
ures in light of the new NAAQS. But, after considering
“the contents of each individual state's submission . . . on
their own merits” and making an individual determination
with respect to each SIP, EPA disagreed. Id., at 9354.
After making its individual determinations, EPA aggre-
gated its disapprovals into one omnibus Federal Register
rule. Id., at 9337–9338. The rule began by describing
EPA's “4-step framework” for evaluating SIP submissions,
although EPA noted that it had also permitted States to
“presen[t] alternative approaches.” Id., at 9338.
1
EPA
then provided for each State a “brief, high level overview”
1
Under EPA's four-step framework, the agency (1) identifes monitoring
sites that will likely have diffculty meeting the NAAQS; (2) identifes
upwind States that “impact those air quality problems . . . suffciently such
that the states are considered `linked' and therefore warrant further re-
view and analysis”; (3) “identif[ies] the emissions reductions necessary (if
any) . . . to eliminate each linked upwind state's signifcant contribution”
to excess ozone at the downwind monitoring sites; and (4) “adopt[s] perma-
nent and enforceable measures needed to achieve those emissions reduc-
tions.” 88 Fed. Reg. 9338.
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as: 605 U. S. 609 (2025)
617
Opinion of the Court
of its “evaluation and key bases for disapproval,” while di-
rec
ting readers to the “relevant Federal Register notifca-
tions of proposed disapproval for each state” and certain
other documents for the “full basis for the EPA's disapprov-
als.” Id., at 9354 (boldface deleted).
In its rule, EPA also asserted that its disapprovals would
be reviewable only in the D. C. Circuit. According to EPA,
the rule was a nationally applicable action under § 7607(b)(1).
Id., at 9380. Alternatively, EPA made a fnding that, if the
rule was only locally or regionally applicable, then it fell
within the “ `nationwide scope or effect' ” exception. EPA
identifed as qualifying determinations of nationwide scope
or effect its use of “the same, nationally consistent 4-step . . .
framework,” as well as its evaluation of States' alternative
approaches “with an eye to ensuring national consistency
and avoiding inconsistent or inequitable results.” Id., at
9380–9381.
D isregardi ng EPA's conclusi ons, St ates and energ y-
industry petitioners challenged EPA's SIP disapprovals in
the regional Circuits. EPA moved to dismiss these chal-
lenges or to transfer them to the D. C. Circuit, but its efforts
have been largely unsuccessful. Of the fve Circuits to re-
solve EPA's motions, four have found that regional Circuit
review is proper.
2
Only the Tenth Circuit disagreed, granting EPA's motion
to transfer suits brought by the States of Oklahoma and
Utah and by industry petitioners (collectively, petitioners).
93 F. 4th 1262, 1264 (2024). In its view, EPA's omnibus rule
disapproving the 21 SIPs constituted a single, nationally ap-
plicable action. Id., at 1266. Rejecting petitioners' conten-
tion that each individual SIP disapproval constitutes its own
“action,” the Tenth Circuit concluded that the relevant “ac-
2
See West Virginia v. EPA, 90 F. 4th 323, 325 (CA4 2024); Texas v. EPA,
132 F. 4th 808, 830 (CA5 2025); Kentucky v. EPA, 123 F. 4th 447, 452 (CA6
2024); Order in Arkansas v. EPA, No. 23–1320, ECF Doc. 5269098 (CA8,
Apr. 25, 2023).
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618 OKLAH
OMA v. EPA
Opinion of the Court
tion” is simply whatever EPA has “chosen to issue.” Id., at
1267.
Thus, because EPA had grouped its disapprovals into
a single rule, that rule constituted the “action” at hand. See
id., at 1266–1267. And, the Tenth Circuit concluded, this ac-
tion was nationally applicable given both its geographical
breadth and the nature of its analysis: EPA's rule covered
“21 states across the country” and refected EPA's “appli[ca-
tion of] a uniform statutory interpretation and common ana-
lytical methods.” Id., at 1266. The Tenth Circuit accord-
ingly transferred petitioners' challenges to the D. C. Circuit.
Id., at 1264. We granted certiorari to review that transfer
decision. 604 U. S. 997 (2024).
II
Applying our Calumet framework, we begin with the frst
step of the § 7607(b)(1) inquiry. As explained, at this step,
we must identify the relevant EPA “action” and then decide
whether it is nationally applicable or only locally or region-
ally applicable. 605 U. S., at 636–639. We conclude that the
EPA “action” in these cases is not EPA's omnibus rule, but
rather its individual denials of the Oklahoma and Utah SIPs.
Clearly, these denials are locally or regionally applicable.
A
As we recognized in Calumet, “[b]ecause § 7607(b)(1) pegs
venue to the scope of the EPA action being challenged, our
threshold task is to identify the `action' at issue.” Id., at
636. Only when we understand the relevant “action” can
we decide whether it is nationally applicable or locally or
regionally applicable—that is, whether it facially applies
“throughout the entire country, or only to particular locali-
ties or regions.” Id., at 638. Here, as in Calumet, our reso-
lution of the threshold question effectively resolves the
proper classifcation.
3
3
As in Calumet, we need not decide the precise line between a “na-
tionally applicable” and a “locally or regionally applicable” action un-
der § 7607(b)(1). That question may raise diffcult questions in edge cases
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as: 605 U. S. 609 (2025)
619
Opinion of the Court
An “action” under § 7607(b)(1) is a “particular exercis[e] of
EP
A authority undertaken pursuant to [a] particular CAA
provisio[n].” Id., at 637. We thus determine the relevant
“action” by reference to the CAA provision under which
EPA has acted. This focus on the operative CAA provision
means that the relevant “action” will not necessarily track
how EPA has presented its decision. For example, in Calu-
met, we held that, whenever EPA denies a small refnery's
petition for an exemption from the CAA's renewable fuel
program, each individual exemption denial constitutes its
own “action” because § 7545(o)(9)(B) defnes EPA's role—
“ `evaluating a petition' ” and “ `act[ing] on' ” it—on a petition-
specifc basis. Id., at 639 (alteration omitted). That statu-
tory denomination controls even if EPA chooses to resolve
multiple petitions in one fell swoop, as it did in Calumet.
Id., at 640.
Here too, we conclude that each EPA SIP disapproval con-
stitutes its own “action.” We therefore reject EPA's con-
tention, adopted by the Tenth Circuit, that EPA's omnibus
rule should be treated as a single “action.” Instead, we
have before us two distinct “actions”—EPA's respective dis-
approvals of the Oklahoma and Utah SIPs.
Section 7607(b)(1) simplifes our analysis of this issue.
The CAA enumerates an individual SIP approval as an ex-
ample of a locally or regionally applicable action, unlike in
Calumet, where we dealt with an EPA decision that did not
fall within any of § 7607(b)(1)'s enumerated actions. Section
7607(b)(1) provides:
“A petition for review of the Administrator's action in
approving or promulgating any implementation plan
under section 7410 of this title . . . , [other enumerated
examples], . . . or any other fnal action of the Adminis-
trator under this chapter (including any denial or disap-
g iven the bi nary nature of these categor ies. See 605 U. S., at 639,
n. 3.
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620 OKLAH
OMA v. EPA
Opinion of the Court
proval by the Administrator under subchapter I) which
is
locally or regionally applicable may be fled only in
the United States Court of Appeals for the appropriate
circuit.”
A SIP is an “implementation plan under section 7410,” and
§ 7607(b)(1)—in referring expressly to EPA's “action in ap-
proving . . . any implementation plan” under that provision—
makes clear that each EPA SIP approval is its own action.
It follows that each EPA SIP disapproval is also its own
action. EPA undertakes SIP disapprovals pursuant to
the same CAA authority underlying its SIP approvals.
Namely, § 7410 directs “[e]ach State” to “adopt and submit
[to EPA] a plan” for NAAQS implementation, and in turn
directs EPA to either “approve such submittal” or “disap-
prove” it. §§ 7410(a)(1), (k). Thus, EPA's approvals and
disapprovals are opposite sides of the same coin. As § 7410's
SIP-specifc focus makes clear, and § 7607(b)(1)'s enumeration
confrms, the CAA treats both individual SIP approvals and
individual SIP disapprovals as discrete actions. Thus, we
have before us two EPA actions—EPA's disapprovals of the
Oklahoma and Utah SIPs.
These two disapprovals are undisputedly locally or region-
ally applicable actions. A SIP is a state-specifc plan, so an
EPA disapproval on its face applies only to the State that
proposed the SIP. And, the CAA recognizes this limited
scope in enumerating a SIP approval as a locally or region-
ally applicable action. § 7607(b)(1). If anything, EPA's de-
cision on an individual SIP “is the prototypical `locally or
regionally applicable' action,” as courts have recognized and
even EPA acknowledges. American Road & Transp.
Builders Assn. v. EPA, 705 F. 3d 453, 455 (CADC 2013)
(majority opinion of Kavanaugh, J.); see Brief for Respond-
ents 25.
4
4
We leave for another day the meani ng of the parenthetica l i n
§ 7607(b)(1), which specifes that “any other fnal action . . . (including any
denial or disapproval by the Administrator under subchapter I) which is
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B
EP
A's and the Tenth Circuit's contrary arguments do not
survive scrutiny. EPA largely reprises the arguments it
made in Calumet, and we reject those arguments for the
reasons explained there. 605 U. S., at 640–642. In short,
§ 7607(b)(1) “makes the CAA's framing of the relevant `ac-
tion' controlling, regardless of how EPA chooses to package
its decisions in the Federal Register.” Id., at 638. Thus,
although EPA was free to aggregate its SIP disapprovals
into one rule, that aggregation has no signifcance for venue
purposes.
The Tenth Circuit's endorsement of EPA's positi on is
equally unpersuasive. On its view, we must accept EPA's
framing of the relevant “action” because EPA's “action” is
just whatever it has “chosen to issue.” 93 F. 4th, at 1267.
But, that reasoning fails to grapple with what § 7607(b)(1)
means by that word. In context, § 7607(b)(1) defnes the rel-
evant “action” by reference to the underlying CAA provi-
sion, not EPA's stylization. Calumet, 605 U. S., at 637;
supra, at 619.
Nor can the Tenth Circuit deem EPA's actions nationally
applicable based on EPA's use of a “uniform statutory inter-
pretation and common analytical methods.” 93 F. 4th, at
1266. The “applicability” of an action turns on its formal
geographical scope: An action “applies” nationally only if, on
its face, it has binding effect throughout the country. Calu-
met, 605 U. S., at 638–639. In contrast, EPA's interpretive
and analytical methodology goes to its underlying reasoning.
That component matters only at the second § 7607(b)(1) step,
where one prerequisite for D. C. Circuit review is that a lo-
cally or regionally applicable action nonetheless be “based
on a determination of nationwide scope or effect.” We
locally or regionally applicable” is subject to the default of regional Circuit
review. Because we hold that EPA's SIP disapprovals are locally or re-
gionally applicable in any event, we need not consider petitioners' argu-
ment that this parenthetical makes all denials or disapprovals under sub-
chapter I of the CAA locally or regionally applicable actions.
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would make a hash of the CAA's venue framework if we
looked
to the basis for EPA's actions at the frst step too.
III
Because EPA's SIP disapprovals are only locally or region-
ally applicable, we move to the second step of the § 7607(b)(1)
inquiry. At this step, “we ask whether the `nationwide
scope or effect' exception applies to override the default of
regional Circuit review for locally or regionally applicable
actions.” Id., at 642. We hold that it does not: The excep-
tion does not apply here, so these cases properly belong in a
regional Circuit.
Our analysis turns on the frst of the “nationwide scope or
effect” exception's two requirements. That exception ap-
plies only if the action at issue (1) “is based on a determina-
tion of nationwide scope or effect,” and (2) “in taking such
action [EPA] fnds and publishes that such action is based
on such a determination.” § 7607(b)(1). Here, the second
requirement is plainly satisfed: EPA included in its Federal
Register notice an express fnding that its SIP disapprovals
were “based on a determination of `nationwide scope or
effect.' ” 88 Fed. Reg. 9380. Thus, our task is to decide
whether that fnding was correct.
We hold that EPA's SIP disapprovals were not based on
any determination of nationwide scope or effect. As we ex-
plained in Calumet, this requirement is met only if “a justif-
cation of nationwide breadth is the primary explanation for
and driver of EPA's action.” 605 U. S., at 645. But, such a
justifcation “does not rise to this level if EPA also relied in
signifcant part on other, `intensely factual' considerations,
or if the key driver of EPA's action is otherwise debatable.”
Ibid. EPA's disapprovals of the Oklahoma and Utah SIPs
fall into the latter category.
EPA's omnibus rule makes clear that its SIP disapprovals
were based on “a number of intensely factual determina-
tions” particular to the State at issue. Texas v. EPA, 829
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623
Opinion of the Court
F. 3d 405, 421 (CA5 2016). As EPA explained, it evaluated
the
contents of each SIP “on their own merits,” “consider-
[ing] the facts and information . . . available to the state at
the time of its submission,” as well as more recent informa-
tion regarding that State's circumstances. 88 Fed. Reg.
9354. From this state-specifc analysis, EPA produced for
each State a list of “bases for disapproval,” ibid., with each
list “giving a unique mixture of reasons,” West Virginia v.
EPA, 90 F. 4th 323, 330 (CA4 2024). For example, as to
Oklahoma, EPA rejected its attempt to disclaim responsibil-
ity for certain emissions in Texas, while also faulting it for
providing an “insuffcient evaluation of additional emissions
control opportunities.” 88 Fed. Reg. 9359. And, as to
Utah, EPA found that the State had inadequately justifed
its attempt to discount certain emissions in Colorado, while
also “fnd[ing] technical and legal faws in the State's argu-
ments” regarding various emissions considerations. Id., at
9360. Based on these and other reasons, EPA concluded
that each State had failed to submit a SIP with “the neces-
sary provisions to eliminate emissions” consistent with that
State's Good Neighbor obligations. 87 Fed. Reg. 9824, 31483
(2022).
This state-specifc analysis contrasts sharply with EPA's
justifcations in Calumet, where we found the “nationwide
scope or effect” exception triggered. There, EPA made two
determinations that applied uniformly to all small refneries
across the country, which it used to reach a presumptive con-
clusion as to how the exemption petitions before it should be
resolved. 605 U. S., at 646–647. EPA considered refnery-
specifc facts only to “confrm that it had no reason to depart
from its presumptive disposition.” Id., at 647. In that cir-
cumstance, we explained, EPA's national determinations con-
stituted “the most important parts of its reasoning ” and “the
primary driver of its decision.” Ibid.
Here, in contrast, no nationwide factor all but settles
EPA's ultimate decisions. Instead, EPA disapproved Okla-

624 OKLAH
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homa's and Utah's SIPs after conducting predominantly fact-
i
ntensive, state-specifc analysis.
The determinations that EPA proffers as the basis of its
disapprovals only reinforce this conclusion. Before this
Court, EPA points to four determinations: (1) its use of “up-
dated, 2016-based modeling as the `primary' basis for its `as-
sessment of air quality conditions and pollution contribu-
tion' ”; (2) its application of “a 1% contribution threshold
across all States to assess whether a State contributed more
than a de minimis amount of ozone pollution downwind”;
(3) its “determin[ation] that the relative contributions of
other States or countries could not excuse a State from ana-
lyzing whether its own emissions `signifcantly' contribute to
downwind nonattainment”; and (4) its position that an up-
wind “State cannot rely on emission-reduction measures that
are not actually incorporated into its state plan.” Brief for
Respondents 34–35. We agree with EPA that these conclu-
sions qualify as determinations of nationwide scope or effect,
in that they are conclusions that apply nationwide, either for-
mally or as a practical matter given EPA's rejection of alterna-
tive approaches. But, these conclusions are at most heuris-
tics that aided EPA's analysis, as opposed to the primary
drivers of its disapprovals. None of these determinations,
either alone or in combination, makes clear why EPA con-
cluded that Oklahoma and Utah had produced inadequate pro-
posals for compliance with their Good Neighbor obligations.
5
Take, for example, EPA's use of the 1% contribution
threshold. This threshold—which is triggered whenever an
upwind State contributes at least 1% of the permissible
5
The determinations that EPA invokes before this Court differ from the
ones that it cited in its original fnding, where it focused primarily on its
use of a “consistent 4-step . . . framework” to analyze the SIPs. 88 Fed.
Reg. 9380–9381; supra, at 617. Because we fnd the determinations EPA
currently invokes to be inadequate, we need not decide whether EPA's
shift in position raises a preservation problem. See EPA v. Calumet
Shreveport Refning, L.L.C., 605 U. S. 627, 646, n. 4 (2025).
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ozone level to a downwind State—refers to EPA's measure
of
when an upwind State becomes “ `linked' to a downwind
air quality problem,” so as to implicate potential Good Neigh-
bor obligations. 88 Fed. Reg. 9342; see n. 1, supra. EPA
used this threshold only for “screening ” purposes: Where the
threshold was triggered, EPA would “further evaluate” the
upwind State's emissions, to assess whether those emissions
require ameliorative steps under the CAA. 88 Fed. Reg.
9342, 9371. But, this kind of analytical guidepost cannot be
deemed the primary driver of EPA's ultimate conclusion that
Oklahoma's and Utah's SIPs were defcient. As EPA does
not dispute, even after it made its threshold determination,
“there was still a lot of work to be done” before EPA could
issue its disapprovals. Tr. of Oral Arg. 38. In that circum-
stance, we cannot say that the “nationwide scope or effect”
exception applies.
6
***
The Tenth Circuit erred in holding that petitioners' chal-
lenges should be reviewed in the D. C. Circuit. EPA's disap-
provals of the Oklahoma and Utah SIPs are locally or region-
ally applicable actions. And, these cases are not ones where
the “nationwide scope or effect” exception applies. Accord-
ingly, as with most locally or regionally applicable actions,
petitioners' challenges can be heard only in a regional Cir-
cuit. The judgment of the Court of Appeals is reversed, and
the cases are remanded for further proceedings consistent
with this opinion.
It is so ordered.
Justice Alito took no part in the consideration or deci-
sion of these cases.
6
EPA's case for the exception's applicability rests on arguments that we
rejected in Calumet. Most notably, we rejected EPA's position that its
action is “based on” a qualifying determination so long as that determina-
tion supplies a but-for cause. See id., at 644–645. We need not revisit
here the problems with EPA's premise.
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Gorsuch, J., concurring in judgment
Justice Gorsuch, with whom The Chief Justice joins,
concurr
ing in the judgment.
The Court holds that the proper venue for this litigation
lies in an appropriate regional circuit, not in the D. C. Circuit.
I agree. As I explain in today's companion case, however,
the Court and I arrive at that conclusion by different paths.
See EPA v. Calumet Shreveport Refning, L.L.C., 605 U. S.
627, 662–663 (2025) (Gorsuch, J., dissenting). Accordingly,
I am unable to join the Court's opinion, but I am pleased to
concur in its judgment.
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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