CHAO, SECRETARY OF LABOR v. MALLARD BAY DRILLING, INC.

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235 OCTOBER TERM, 2001
Syllabus
CHAO, SECRETARY OF LABOR v. MALLARD BAY
DRILLING, INC.
certiorari to the united states court of appeals for
the fifth circuit
No. 00–927. Argued October 31, 2001—Decided January 9, 2002
While Rig 52, respondent’s oil and gas exploration barge, was drilling a
well in Louisiana’s territorial waters, an explosion on board killed or
injured several workers. Pursuant to its statutory authority, the
United States Coast Guard investigated the incident, but did not accuse
respondent of violating any of its regulations. Indeed, the Coast Guard
noted that the barge was an “uninspected vessel,” see 46 U. S. C.
§ 2101(43), as opposed to an “inspected vessel” subject to comprehensive
Coast Guard regulation, see § 3301. Subsequently, the Occupational
Safety and Health Administration (OSHA) cited respondent for viola-
tions of the Occupational Safety and Health Act of 1970 (OSH Act or
Act) and its regulations. Respondent challenged OSHA’s jurisdiction
to issue the citations on the grounds that Rig 52 was not a “workplace”
under § 4(a) of the Act and that § 4(b)(1) of the Act pre-empted OSHA
jurisdiction because the Coast Guard had exclusive authority to pre-
scribe and enforce occupational safety and health standards on vessels
such as Rig 52. In rejecting both challenges, the Administrative Law
Judge found that Rig 52 was a “workplace” under the Act and held that
the Coast Guard had not pre-empted OSHA’s jurisdiction, explaining
that there was no industry-wide exemption from OSHA regulations for
uninspected vessels and no Coast Guard regulation specifically regulat-
ing the citations’ subject matter. The Occupational Safety and Health
Review Commission issued a final order assessing a penalty against re-
spondent. Without addressing the § 4(a) issue, the Fifth Circuit re-
versed, holding that the Coast Guard’s exclusive jurisdiction over the
regulation of seamen’s working conditions aboard vessels such as Rig 52
precluded OSHA’s regulation under § 4(b)(1), and that this pre-emption
encompassed both inspected and uninspected vessels.
Held:
1. Because the Coast Guard has neither affirmatively regulated the
working conditions at issue, nor asserted comprehensive regulatory ju-
risdiction over working conditions on uninspected vessels, it has not
exercised its authority under § 4(b)(1). The OSH Act does not apply to
working conditions as to which other federal agencies “exercise” statu-
tory authority to prescribe or enforce occupational safety and health

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236 CHAO v. MALLARD BAY DRILLING, INC.
Syllabus
standards or regulations. § 4(b)(1), 29 U. S. C. § 653(b)(1). Congress’
use of “exercise” makes clear that mere possession by another federal
agency of unexercised authority is insufficient to displace OSHA’s juris-
diction. Furthermore, another federal agency’s minimal exercise of
some authority over certain vessel conditions does not result in com-
plete pre-emption of OSHA jurisdiction. To determine whether Coast
Guard regulations have pre-empted jurisdiction over Rig 52’s working
conditions, it is thus necessary to examine the contours of the Coast
Guard’s exercise of its statutory authority. With respect to inspected
vessels, the parties do not dispute that OSHA’s regulations have been
pre-empted because the Coast Guard has exercised its broad statutory
authority over workers’ occupational health and safety, 46 U. S. C.
§ 3306. Indeed, OSHA and the Coast Guard signed a Memorandum of
Understanding recognizing that the Coast Guard has displaced OSHA’s
jurisdiction over all working conditions on inspected vessels, including
those not addressed by specific regulations. In contrast, the Coast
Guard’s regulatory authority over uninspected vessels is more limited.
Its general maritime regulations do not address the occupational safety
and health concerns faced by inland drilling operations on such vessels
and, thus, do not pre-empt OSHA’s authority in this case. And, al-
though the Coast Guard has engaged in a limited exercise of its author-
ity to regulate specific working conditions on certain types of unin-
spected vessels, respondent has not identified any specific regulations
addressing the types of risk and vessel at issue here. Pp. 240–245.
2. Rig 52 was a “workplace” under § 4(a) of the Act. It was located
within a geographic area described in § 4(a)—a State—and § 4(a) at-
taches no significance to the fact that it was anchored in navigable
waters. P. 245.
212 F. 3d 898, reversed.
Stevens, J., delivered the opinion of the Court, in which all other
Members joined, except Scalia, J., who took no part in the decision of
the case.
Matthew D. Roberts argued the cause for petitioner.
With him on the briefs were Solicitor General Olson, Acting
Solicitor General Underwood, Deputy Solicitor General
Kneedler, Judith E. Kramer, Allen H. Feldman, Nathaniel
I. Spiller, Ellen L. Beard, Edward D. Sieger, James S. Car-
michael, and Robert F. Duncan.

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237 Cite as: 534 U. S. 235 (2002)
Opinion of the Court
Patrick J. Veters argued the cause for respondent. With
him on the brief was John L. Duvieilh.*
Justice Stevens delivered the opinion of the Court.
Respondent operates a fleet of barges used for oil and gas
exploration. On April 9, 1997, one of those barges, “Rig 52,”
was towed to a location in the territorial waters of Louisiana,
where it drilled a well over two miles deep. On June 16,
1997, when the crew had nearly completed drilling, an explo-
sion occurred, killing four members of the crew and injuring
two others. Under United States Coast Guard regulations,
the incident qualified as a “marine casualty” because it in-
volved a commercial vessel operating “upon the navigable
waters of the United States.” 46 CFR § 4.03–1 (2000).
Pursuant to its statutory authority, the Coast Guard con-
ducted an investigation of the casualty. See 46 U. S. C.
§§ 6101–6104, 6301–6308 (1994 ed. and Supp. V).1 The re-
sulting report was limited in scope to what the Coast Guard
described as “purely vessel issues,” and noted that the Coast
Guard “does not regulate mineral drilling operations in state
waters, and does not have the expertise to adequately ana-
lyze all issues relating to the failure of an oil/natural gas
well.” App. to Pet. for Cert. 24a. The Coast Guard deter-
mined that natural gas had leaked from the well, spread
throughout the barge, and was likely ignited by sparks in the
pump room. The report made factual findings concerning
the crew’s actions, but did not accuse respondent of violating
any Coast Guard regulations. Indeed, the report noted the
*Jeffrey Robert White and Frederick M. Baron filed a brief for the As-
sociation of Trial Lawyers of America as amicus curiae urging reversal.
Briefs of amici curiae urging affirmance were filed for the American
Waterways Operators by Barbara L. Holland and Alan P. Sherbrooke; for
the Associated General Contractors of America et al. by Charles T. Car-
roll, Jr., and Carl Larsen Taylor; and for the Transportation Institute by
John Longstreth.
1 Unless otherwise noted, all United States Code references in this opin-
ion are to the 1994 edition.

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238 CHAO v. MALLARD BAY DRILLING, INC.
Opinion of the Court
limits of the Coast Guard’s regulation of vessels such as Rig
52: The report explained that, although Rig 52 held a Coast
Guard Certificate of Documentation, it had “never been
inspected by the Coast Guard and is not required to hold
a Certificate of Inspection or be inspected by the Coast
Guard.” Id., at 27a. In Coast Guard terminology, Rig 52
was an “uninspected vessel,” see 46 U. S. C. § 2101(43), as
opposed to one of the 14 varieties of “inspected vessels” sub-
ject to comprehensive Coast Guard regulation, see 46 U. S. C.
§ 3301 (1994 ed. and Supp. V).
Based largely on information obtained from the Coast
Guard concerning this incident, the Occupational Safety and
Health Administration (OSHA) cited respondent for three vi-
olations of the Occupational Safety and Health Act of 1970
(OSH Act or Act), 84 Stat. 1590, as amended, 29 U. S. C. § 651
et seq. (1994 ed. and Supp. V), and the Act’s implementing
regulations. The citations alleged that respondent failed
promptly to evacuate employees on board the drilling rig;
failed to develop and implement an emergency response plan
to handle anticipated emergencies; and failed to train em-
ployees in emergency response. No. 97–1973, 1998 WL
917067, *1 (OSHRC, Dec. 28, 1998). Respondent did not
deny the charges, but challenged OSHA’s jurisdiction to
issue the citations on two grounds: that Rig 52 was not a
“workplace” within the meaning of § 4(a) of the Act; 2 and
that § 4(b)(1) of the Act pre-empted OSHA jurisdiction be-
cause the Coast Guard had exclusive authority to prescribe
2 Section 4(a) of the Act, as codified in 29 U. S. C. § 653(a), provides in
part: “This chapter shall apply with respect to employment performed in
a workplace in a State, the District of Columbia, the Commonwealth of
Puerto Rico, the Virgin Islands, American Samoa, Guam, the Trust Terri-
tory of the Pacific Islands, Wake Island, Outer Continental Shelf lands
defined in the Outer Continental Shelf Lands Act, Johnston Island, and
the Canal Zone” (citation omitted).

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Opinion of the Court
and enforce standards concerning occupational safety and
health on vessels in navigable waters.3
The Administrative Law Judge (ALJ) rejected both juris-
dictional challenges. Finding that respondent’s “employees
were not performing navigational-related activities” and that
Rig 52 “was stationary and within the territorial boundaries
of the State of Louisiana,” he concluded that Rig 52 was a
“workplace” within the meaning of the Act. Id., at *3. The
ALJ then held that the Coast Guard had not pre-empted
OSHA’s jurisdiction under § 4(b)(1), explaining that respond-
ent had identified no basis for an “industry-wide exemption
from OSHA regulations” for uninspected vessels, and had
failed to identify any Coast Guard regulation “specifically
regulat[ing]” the subject matter of the citations. Id., at *4.
In the ALJ’s view, another federal agency cannot pre-empt
OSHA’s jurisdiction under § 4(b)(1) unless that agency exer-
cises its statutory authority to regulate a particular working
condition: Mere possession of the power to regulate is not
enough.4 The Occupational Safety and Health Review Com-
mission declined review of the ALJ’s decision and issued a
final order assessing a penalty against respondent of $4,410
per citation. Id., at *1.
3 Section 4(b)(1) of the Act, as codified in 29 U. S. C. § 653(b)(1), provides:
“Nothing in this chapter shall apply to working conditions of employees
with respect to which other Federal agencies, and State agencies acting
under [§ 274 of the Atomic Energy Act of 1954], exercise statutory author-
ity to prescribe or enforce standards or regulations affecting occupational
safety and health.”
4 According to the ALJ: “The term ‘exercise,’ as used in § 4(b)(1), re-
quires an actual assertion of regulatory authority as opposed to a mere
possession of authority. OSHA jurisdiction will be preempted only as to
those working conditions actually covered by the agency regulations. . . .
The OSHA citation alleges that [respondent] failed to evacuate employees
and failed to have an emergency response plan. [Respondent] does not
argue or identify any similar requirement enforced by the U. S. Coast
Guard.” No. 97–1973, 1998 WL 917067, *3–4 (OSHRC, Dec. 28, 1998).

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Opinion of the Court
Without reaching the question whether Rig 52 was a
“workplace” under § 4(a) of the OSH Act, the United States
Court of Appeals for the Fifth Circuit reversed. It held
that the Coast Guard “has exclusive jurisdiction over the
regulation of working conditions of seamen aboard vessels
such as [Rig 52], thus precluding OSHA’s regulation under
Section 4(b)(1) of the OSH Act.” 212 F. 3d 898, 900 (2000).
The Court of Appeals determined that this pre-emption en-
compassed uninspected vessels such as Rig 52, as well as
inspected ones, explaining that the Coast Guard “has in fact
exercised” its “authority to issue safety regulations for unin-
spected vessels”—as § 4(b)(1) requires for pre-emption. Id.,
at 901 (stating, with respect to uninspected vessels, that the
Coast Guard has issued regulations concerning “life preserv-
ers and other lifesaving equipment; emergency alerting and
locating equipment; fire extinguishing equipment; backfire
flame control; ventilation of tanks and engine spaces; cook-
ing, heating, and lighting systems; safety orientation and
emergency instructions; action required after an accident;
and signaling lights”). However, the court conceded that
“[b]ecause a drilling barge is not self-propelled, some of these
regulations, by their nature, do not apply to [Rig 52].” Id.,
at 901, n. 6.
Because other Courts of Appeals have construed the pre-
emptive force of § 4(b)(1) more narrowly than did the Fifth
Circuit, akin to the interpretation adopted by the ALJ in
this case,5 we granted certiorari to resolve the conflict. 531
U. S. 1143 (2001). We reverse, as the statute requires us
to do.
The OSH Act imposes on covered employers a duty to pro-
vide working conditions that “are free from recognized haz-
ards that are causing or are likely to cause death or serious
5 See Herman v. Tidewater Pacific, Inc., 160 F. 3d 1239 (CA9 1998); In re
Inspection of Norfolk Dredging Co., 783 F. 2d 1526 (CA11), cert. denied,
479 U. S. 883 (1986); Donovan v. Red Star Marine Services, Inc., 739 F. 2d
774 (CA2 1984), cert. denied, 470 U. S. 1003 (1985).

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bodily harm” to their employees, as well as an obligation to
comply with safety standards promulgated by the Secretary
of Labor. 29 U. S. C. §§ 654(a)(1), (2).6 The coverage of the
Act does not, however, extend to working conditions that are
regulated by other federal agencies. To avoid overlapping
regulation, § 4(b)(1) of the Act, as codified in 29 U. S. C.
§ 653(b)(1), provides:
“Nothing in this [Act] shall apply to working condi-
tions of employees with respect to which other Federal
agencies . . . exercise statutory authority to prescribe or
enforce standards or regulations affecting occupational
safety and health.” (Emphasis added.)
Congress’ use of the word “exercise” makes clear that, con-
trary to respondent’s position, see, e. g., Tr. of Oral Arg. 39,
mere possession by another federal agency of unexercised
authority to regulate certain working conditions is insuffi-
cient to displace OSHA’s jurisdiction. Furthermore, an-
other federal agency’s minimal exercise of some authority
over certain conditions on vessels such as Rig 52 does not
result in complete pre-emption of OSHA jurisdiction, be-
cause the statute also makes clear that OSHA is only pre-
empted if the working conditions at issue are the particular
ones “with respect to which” another federal agency has reg-
ulated, and if such regulations “affec[t] occupational safety or
health.” § 653(b)(1).7 To determine whether Coast Guard
6 The Secretary of Labor has delegated her authority under the Act to
the Assistant Secretary for Occupational Safety and Health, who heads
OSHA. See 65 Fed. Reg. 50017 (2000).
7 The Circuits have recognized at least two approaches for defining
“working conditions” under § 4(b)(1). A “hazard-based” approach, which
the Secretary of Labor endorses, focuses on “the particular physical and
environmental hazards encountered by an employee” on the job. Brief
for Petitioner 24; see, e. g., Donovan v. Red Star Marine Services, Inc., 739
F. 2d, at 779–780. In contrast, an “area-based” approach defines “working
conditions” as the “area in which an employee customarily goes about his
daily tasks.” Southern R. Co. v. Occupational Safety and Health Review

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242 CHAO v. MALLARD BAY DRILLING, INC.
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regulations have pre-empted OSHA’s jurisdiction over the
working conditions on Rig 52, it is thus necessary to examine
the contours of the Coast Guard’s exercise of its statutory
authority, not merely the existence of such authority.
Congress has assigned a broad and important mission to
the Coast Guard. Its governing statute provides, in part:
“The Coast Guard . . . shall administer laws and promul-
gate and enforce regulations for the promotion of safety
of life and property on and under the high seas and wa-
ters subject to the jurisdiction of the United States cov-
ering all matters not specifically delegated by law to
some other executive department . . . .” 14 U. S. C. § 2
(2000 ed.).
Under this provision, the Coast Guard possesses authority
to promulgate and enforce regulations promoting the safety
of vessels anchored in state navigable waters, such as Rig 52.
As mentioned above, however, in defining the Coast Guard’s
regulatory authority, Congress has divided the universe of
vessels into two broad classes: “inspected vessels” and “unin-
spected vessels.” In 46 U. S. C. § 3301 (1994 ed. and Supp.
V), Congress has listed 14 types of vessels that are “subject
to inspection” by the Coast Guard pursuant to a substan-
tial body of rules mandated by Congress.8 In contrast, 46
Comm’n, 539 F. 2d 335, 339 (CA4), cert. denied, 429 U. S. 999 (1976). We
need not choose between these interpretations, however, because the
Coast Guard did not regulate the “working conditions” at issue in this case
under either definition of the term.
8 “The following categories of vessels are subject to inspection under
this part: (1) freight vessels. (2) nautical school vessels. (3) offshore
supply vessels. (4) passenger vessels. (5) sailing school vessels. (6)
seagoing barges. (7) seagoing motor vessels. (8) small passenger ves-
sels. (9) steam vessels. (10) tank vessels. (11) fish processing vessels.
(12) fish tender vessels. (13) Great Lakes barges. (14) oil spill re-
sponse vessels.”

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U. S. C. § 2101(43) defines an “uninspected vessel” as “a
vessel not subject to inspection under section 3301 . . . that
is not a recreational vessel.”
The parties do not dispute that OSHA’s regulations have
been pre-empted with respect to inspected vessels, because
the Coast Guard has broad statutory authority to regulate
the occupational health and safety of seamen aboard in-
spected vessels, 46 U. S. C. § 3306 (1994 ed. and Supp. V), and
it has exercised that authority. Indeed, the Coast Guard
and OSHA signed a “Memorandum of Understanding”
(MOU) on March 17, 1983, evidencing their agreement that,
as a result of the Coast Guard’s exercise of comprehensive
authority over inspected vessels, OSHA “may not enforce
the OSH Act with respect to the working conditions of sea-
men aboard inspected vessels.” 48 Fed. Reg. 11365. The
MOU recognizes that the exercise of the Coast Guard’s au-
thority—and hence the displacement of OSHA jurisdiction—
extends not only to those working conditions on inspected
vessels specifically discussed by Coast Guard regulations,
but to all working conditions on inspected vessels, including
those “not addressed by the specific regulations.” Ibid.
Thus, as OSHA recognized in the MOU, another agency may
“exercise” its authority within the meaning of § 4(b)(1) of the
OSH Act either by promulgating specific regulations or by
asserting comprehensive regulatory authority over a certain
category of vessels.
Uninspected vessels such as Rig 52, however, present an
entirely different regulatory situation. Nearly all of the
Coast Guard regulations responsible for displacing OSHA’s
jurisdiction over inspected vessels, as described in the MOU,
do not apply to uninspected vessels like Rig 52. See 46
U. S. C. § 2101(43). Rather, in the context of uninspected
vessels, the Coast Guard’s regulatory authority—and exer-
cise thereof—is more limited. With respect to uninspected
vessels, the Coast Guard regulates matters related to marine

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244 CHAO v. MALLARD BAY DRILLING, INC.
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safety, such as fire extinguishers, life preservers, engine
flame arrestors, engine ventilation, and emergency locating
equipment. See 46 U. S. C. § 4102 (1994 ed. and Supp. V);
46 CFR pts. 24–26 (2000). Because these general marine
safety regulations do not address the occupational safety and
health concerns faced by inland drilling operations on unin-
spected vessels, they do not pre-empt OSHA’s authority
under § 4(b)(1) in this case. Indeed, as the Court of Appeals
acknowledged, many of these general Coast Guard regula-
tions for uninspected vessels do not even apply to stationary
barges like Rig 52. See 212 F. 3d, at 901, n. 6.
In addition to issuing these general marine safety regula-
tions, the Coast Guard has exercised its statutory authority
to regulate a number of specific working conditions on cer-
tain types of uninspected vessels. For example, the Coast
Guard regulates drilling operations that take place on the
outer continental shelf. See 43 U. S. C. § 1333(a)(1); 33 CFR
pt. 142 (2000). And it is true that some of these more spe-
cific regulations would, pursuant to § 4(b)(1), pre-empt OSHA
regulations covering those particular working conditions and
vessels. But respondent has not identified any specific
Coast Guard regulations that address the types of risk and
vessel at issue in this case: namely, dangers from oil-drilling
operations on uninspected barges in inland waters. Sim-
ply because the Coast Guard has engaged in a limited exer-
cise of its authority to address certain working conditions
pertaining to certain classes of uninspected vessels does
not mean that all OSHA regulation of all uninspected ves-
sels has been pre-empted. See 29 U. S. C. § 653(b)(1) (pre-
emption only extends to working conditions “with respect to
which” other federal agencies have exercised their authority
(emphasis added)). Because the Coast Guard has neither af-
firmatively regulated the working conditions at issue in this
case, nor asserted comprehensive regulatory jurisdiction

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over working conditions on uninspected vessels, the Coast
Guard has not “exercise[d]” its authority under § 4(b)(1).9
We think it equally clear that Rig 52 was a “workplace” as
that term is defined in § 4(a) of the Act. The vessel was
located within the geographic area described in the defini-
tion: “a State,” 29 U. S. C. § 653(a), namely, Louisiana. Noth-
ing in the text of § 4(a) attaches any significance to the fact
that the barge was anchored in navigable waters. Rather,
the other geographic areas described in § 4(a) support a read-
ing of that provision that includes a State’s navigable waters:
for example, § 4(a) covers the Outer Continental Shelf, and
sensibly extends to drilling operations attached thereto.
Cf. 43 U. S. C. § 1333(a)(1).
Accordingly, the judgment of the Court of Appeals is
reversed.
It is so ordered.
Justice Scalia took no part in the decision of this case.
9 The statutory provisions themselves resolve this case, because the
Coast Guard has not “exercise[d]” authority under § 4(b)(1) with respect
to the working conditions at issue here. It is worth noting, however, that
this interpretation of § 4(b)(1)’s pre-emptive scope comports with the OSH
Act’s fundamental purpose: “to assure so far as possible every working
man and woman in the Nation safe and healthful working conditions.” 29
U. S. C. § 651(b). As respondent declared at oral argument, its interpreta-
tion of § 4(b)(1) would mean that if the Coast Guard regulated marine
toilets on Rig 52 and nothing more, any OSHA regulation of the vessel
would be pre-empted. Tr. of Oral Arg. 20. Such large gaps in the regu-
lation of occupational health and safety would be plainly inconsistent with
the purpose of the OSH Act.