Petition for Writ of Certiorari — Suncor Energy (U.S.A.) Inc., et al., Petitioners v. County Commissioners of Boulder County, et al.
Supreme Court briefAug 8, 2025
Ask Donna
What actually matters in this document.
Text
No.
In the Supreme Court of the United States
SUNCOR ENERGY (U.S.A.) INC.; SUNCOR ENERGY
SALES INC.; EXXON MOBIL CORPORATION,
PETITIONERS
v.
COUNTY COMMISSIONERS OF BOULDER COUNTY;
CITY OF BOULDER
ON PETITION FOR A WRIT OF CERTIORARI
TO THE SUPREME COURT OF COLORADO
PETITION FOR A WRIT OF CERTIORARI
THEODORE V. WELLS, JR.
DANIEL J. TOAL
YAHONNES CLEARY
PAUL, WEISS, RIFKIND,
WHARTON & GARRISON LLP
1285 Avenue of the Americas
New York, NY 10019
HUGH QUAN GOTTSCHALK
ERIC L. ROBERTSON
WHEELER TRIGG
O’DONNELL LLP
370 Seventeenth Street,
Suite 4500
Denver, CO 80202
KANNON K. SHANMUGAM
Counsel of Record
WILLIAM T. MARKS
JAKE L. KRAMER
EMMA R. WHITE
PAUL, WEISS, RIFKIND,
WHARTON & GARRISON LLP
2001 K Street, N.W.
Washington, DC 20006
(202) 223-7300
kshanmugam@paulweiss.com
QUESTION PRESENTED
Whether federal law precludes state-law claims seeking relief for injuries allegedly caused by the effects of interstate and international greenhouse-gas emissions on
the global climate.
(I)
CORPORATE DISCLOSURE STATEMENT
Petitioner Suncor Energy (U.S.A.) Inc. is a wholly
owned indirect subsidiary of Suncor Energy Inc. Suncor
Energy Inc. has no parent corporation, and no publicly
traded company owns 10% or more of its stock.
Petitioner Suncor Energy Sales Inc. is a wholly owned
subsidiary of Suncor Energy (U.S.A.) Inc.
Petitioner Exxon Mobil Corporation has no parent
corporation, and no publicly held company owns 10% or
more of its stock.
(II)
RELATED PROCEEDINGS
United States District Court (D. Colo.):
Board of County Commissioners of Boulder County,
et al. v. Suncor Energy (U.S.A.) Inc., et al.,
Civ. No. 18-1672 (Sept. 5, 2019)
United States Court of Appeals (10th Cir.):
Board of County Commissioners of Boulder County,
et al. v. Suncor Energy (U.S.A.) Inc., et al.,
No. 19-1330 (July 7, 2020)
Board of County Commissioners of Boulder County,
et al. v. Suncor Energy (U.S.A.) Inc., et al.,
No. 19-1330 (Feb. 8, 2022)
United States Supreme Court:
Suncor Energy (U.S.A.) Inc., et al. v. Board of
County Commissioners of Boulder County, et al.,
No. 20-783 (May 24, 2021)
Suncor Energy (U.S.A.) Inc., et al. v. Board of
County Commissioners of Boulder County, et al.,
No. 21-1550 (Apr. 24, 2023)
Colorado District Court (Boulder County):
Board of County Commissioners of Boulder County,
et al. v. Suncor Energy (U.S.A.) Inc., et al.,
No. 2018CV30349 (June 21, 2024)
Colorado Supreme Court:
County Commissioners of Boulder County, et al.
v. Suncor Energy USA, Inc., et al.,
No. 24SA206 (May 12, 2025)
(III)
TABLE OF CONTENTS
Page
Opinions below ................................................................................1
Jurisdiction ......................................................................................2
Constitutional provision involved .................................................2
Statement .........................................................................................2
A. Background ........................................................................ 4
B. Facts and procedural history ........................................... 7
Reasons for granting the petition...............................................12
A. The decision below deepens a conflict
on the question presented and is at odds
with the views of the United States .............................. 13
B. The decision below is incorrect ...................................... 22
C. The question presented is important
and warrants the Court’s review in this case .............. 30
Conclusion ......................................................................................34
Appendix A ....................................................................................1a
Appendix B ..................................................................................48a
Appendix C ................................................................................140a
TABLE OF AUTHORITIES
Cases:
American Electric Power Co.
v. Connecticut, 564 U.S. 410 (2011)............ 5, 6, 10, 22-25,
28, 31
American Insurance Association
v. Garamendi, 539 U.S. 396 (2003) ............................. 7, 26
Banco Nacional de Cuba v. Sabbatino,
376 U.S. 398 (1964) .............................................................. 7
Bell v. Cheswick Generating Station,
734 F.3d 188 (3d Cir. 2013),
cert. denied, 572 U.S. 1149 (2014) ................................... 20
Bonaparte v. Tax Court, 104 U.S. 592 (1882) ..................... 23
(V)
VI
Page
Cases—continued:
BP p.l.c. v. Mayor & City Council of Baltimore,
141 S. Ct. 1532 (2021) .......................................................... 9
Brown-Forman Corp. v. Miller,
528 S.W.3d 886 (Ky. 2017) ................................................ 20
Buckman Co. v. Plaintiffs’ Legal Committee,
531 U.S. 341 (2001) ............................................................ 22
City & County of Honolulu v. Sunoco LP,
537 P.3d 1173 (Haw. 2023),
cert. denied, 145 S. Ct. 1111 (2025) ..................... 16, 17, 18
City of Milwaukee v. Illinois,
451 U.S. 304 (1981) ......................................6, 15, 19, 24, 27
City of New York v. Chevron Corp.,
993 F.3d 81 (2d Cir. 2021) ............................... 3-5, 7, 8, 10,
12-18, 23, 25-29
Coventry Health Care of Missouri, Inc.
v. Nevils, 581 U.S. 87 (2017) ...................................... 32, 33
Cox Broadcasting Corp. v. Cohn,
420 U.S. 469 (1975) ........................................................ 2, 32
Dan’s City Used Cars, Inc. v. Pelkey,
569 U.S. 251 (2013) ............................................................ 32
Franchise Tax Board v. Hyatt,
587 U.S. 230 (2019) ........................................................ 5, 23
Freeman v. Grain Processing Corp.,
848 N.W.2d 58 (Iowa),
cert. denied, 574 U.S. 1026 (2014) ................................... 20
Fuld v. Palestine Liberation
Organization, 145 S. Ct. 2090 (2025) .............. 7, 23, 26, 29
Georgia v. Tennessee Copper Co.,
206 U.S. 230 (1907) .............................................................. 6
Goodyear Atomic Corp. v. Miller,
486 U.S. 174 (1988) .............................................................. 2
Illinois v. City of Milwaukee,
731 F.2d 403 (7th Cir. 1984) ........................... 10, 18-20, 27
Illinois v. City of Milwaukee,
406 U.S. 91 (1972) .......................................... 5, 6, 14, 23, 24
VII
Page
Cases—continued:
International Paper Co. v. Ouellette,
479 U.S. 481 (1987) ......................................6, 19, 22, 24, 28
Kansas v. Colorado, 206 U.S. 46 (1907) .............................. 23
Kurns v. Railroad Friction Products Corp.,
565 U.S. 625 (2012) ............................................................ 25
Merrick v. Diageo Americas Supply, Inc.,
805 F.3d 685 (6th Cir. 2015) ............................................. 20
Minnesota v. American Petroleum Institute,
63 F.4th 703 (8th Cir. 2023),
cert. denied, 144 S. Ct. 620 (2024) ................................... 29
Mississippi Power & Light Co. v. Mississippi ex
rel. Moore, 487 U.S. 354 (1988)........................................ 33
National Pork Producers Council v. Ross,
143 S. Ct. 1142 (2023) ........................................................ 23
North Carolina ex rel. Cooper
v. Tennessee Valley Authority,
615 F.3d 291 (4th Cir. 2010) ....................................... 19, 20
Texas Industries, Inc. v. Radcliff
Materials, Inc., 451 U.S. 630 (1981) ................. 4, 5, 22, 27
United States v. Bevans,
16 U.S. (3 Wheat.) 336 (1818) ........................................... 23
United States v. Locke, 529 U.S. 89 (2000) ......................... 22
Zschernig v. Miller, 389 U.S. 429 (1968) ......................... 7, 26
Constitution and statutes:
U.S. Const. Art. VI, cl. 2 .......................................................... 2
Clean Air Act,
42 U.S.C. 7401 et seq. ......................... 3, 6, 7, 10, 11, 14-17,
24-26, 28
42 U.S.C. 7411(b) ............................................................... 25
42 U.S.C. 7411(d) ............................................................... 25
42 U.S.C. 7521(a)(1) .......................................................... 25
42 U.S.C. 7521(a)(2) .......................................................... 25
42 U.S.C. 7521(a)(3)(E)..................................................... 25
42 U.S.C. 7547(a)(1) .......................................................... 25
42 U.S.C. 7547(a)(5) .......................................................... 25
VIII
Page
Statutes—continued:
42 U.S.C. 7571(a)(2)(A) ............................................... 25, 26
Clean Water Act, 33 U.S.C. 1251 et seq. ............. 6, 19, 24, 28
28 U.S.C. 1257(a) ................................................................ 2, 32
Colo. Rev. Stat. § 6-1-105(1) ................................................... 9
Miscellaneous:
Exec. Order No. 14,260 (Apr. 8, 2025) ..................... 21, 31, 32
In the Supreme Court of the United States
No.
SUNCOR ENERGY (U.S.A.) INC.; SUNCOR ENERGY
SALES INC.; EXXON MOBIL CORPORATION,
PETITIONERS
v.
COUNTY COMMISSIONERS OF BOULDER COUNTY;
CITY OF BOULDER
ON PETITION FOR A WRIT OF CERTIORARI
TO THE SUPREME COURT OF COLORADO
PETITION FOR A WRIT OF CERTIORARI
Suncor Energy (U.S.A.) Inc., Suncor Energy Sales
Inc., and Exxon Mobil Corporation respectfully petition
for a writ of certiorari to review the judgment of the Colorado Supreme Court in this case.
OPINIONS BELOW
The opinion of the Colorado Supreme Court (App., infra, 1a-47a) is not yet reported but is available at 2025 WL
1363355. The opinion of the trial court (App., infra, 48a139a) is unreported but is available at 2024 WL 3204275.
(1)
2
JURISDICTION
The judgment of the Colorado Supreme Court was entered on May 12, 2025. The jurisdiction of this Court is
invoked under 28 U.S.C. 1257(a). See Goodyear Atomic
Corp. v. Miller, 486 U.S. 174, 178-180 (1988); Cox Broadcasting Corp. v. Cohn, 420 U.S. 469, 482-483 (1975).
CONSTITUTIONAL PROVISION INVOLVED
Article VI, clause 2, of the United States Constitution
provides:
This Constitution, and the laws of the United States
which shall be made in pursuance thereof; and all treaties made, or which shall be made, under the authority
of the United States, shall be the supreme law of the
land; and the judges in every state shall be bound
thereby, anything in the Constitution or laws of any
State to the contrary notwithstanding.
STATEMENT
This case provides the Court with its best opportunity
yet to resolve one of the most important questions currently pending in the lower courts. Energy companies
that produce and sell fossil fuels are facing numerous lawsuits in state courts across the Nation seeking billions of
dollars in damages for injuries allegedly caused by the
contribution of greenhouse-gas emissions to global climate change. But as the Court has recognized for over a
century, the structure of our constitutional system does
not permit a State to provide relief under state law for injuries allegedly caused by pollution emanating from outside the State. This case presents the question whether
that longstanding principle precludes the state-law claims
in the nationwide climate-change litigation. The answer
to that question is surely yes.
3
This Court has already recognized the importance of
the question presented by calling for the views of the Solicitor General in Sunoco LP v. City & County of Honolulu, No. 23-947. Since the previous Administration filed
its brief in that case, the new Administration has filed a
brief in another climate-change case arguing that federal
law precludes state-law claims seeking relief for similar
climate-change claims. See U.S. Br. at 8-27, Mayor &
City Council of Baltimore v. BP p.l.c., No. 11, Sept. Term
2025 (Md.) (July 15, 2025). The Colorado Supreme
Court’s divided decision below deepens a clear conflict on
that question. Only this Court can resolve it.
Petitioners are energy companies that produce and
sell fossil fuels; respondents are the city of Boulder, Colorado, and the surrounding county. Like numerous other
state and local governments nationwide, respondents filed
this action against petitioners in state court, asserting
claims purportedly arising under state law to recover for
alleged harms caused by the effects of global climate
change.
The trial court denied petitioners’ motion to dismiss,
and a divided Colorado Supreme Court affirmed. The majority acknowledged this Court’s precedents holding that
claims seeking relief for injuries allegedly caused by interstate pollution constitute an inherently federal area exclusively governed by federal law. But the court concluded that, because Congress had displaced the preexisting federal common law in this area by enacting the Clean
Air Act, state tort law presumptively could regulate interstate emissions. In so holding, the court expressly declined to follow the Second Circuit’s decision in City of
New York v. Chevron Corp., 993 F.3d 81 (2021), which held
that it was “too strange to seriously contemplate” that
4
Congress’s enactment of legislation in an inherently federal area would “suddenly” make state law “presumptively competent” to apply. Id. at 99.
The dissenting justices agreed with the Second Circuit’s analysis. And in so doing, they expressed concern
that the majority’s decision gave Boulder and other Colorado municipalities “the green light to act as [their] own
republic” by regulating on an interstate and international
level. App., infra, 25a. That result could “interfere” with
the federal government’s policies and “contribute to a
patchwork of inconsistent local standards that will beget
regulatory chaos.” Id. at 47a. The dissenting justices “respectfully urge[d]” this Court to “take up this issue.” Id.
at 46a.
There are few, if any, more consequential questions
pending in the lower courts concerning the relationship
between state and federal law. The Colorado Supreme
Court’s decision was incorrect, and it provides this Court
with the opportunity definitively to address whether the
state-law claims asserted by dozens of States and municipalities can even proceed—and to do so before the energy
industry is threatened with potentially enormous judgments.
Boulder, Colorado, cannot make energy policy for the
entire country. The Court should grant review and clarify
that state law cannot impose the costs of global climate
change on a subset of the world’s energy producers chosen by a single municipality. At a minimum, the Court
may wish to call for the views of the Solicitor General in
order to receive the perspective of the new Administration on whether certiorari should be granted.
A. Background
1. As this Court has long explained, there are certain
areas in which “our federal system does not permit the
5
controversy to be resolved under state law.” Texas Industries, Inc. v. Radcliff Materials, Inc., 451 U.S. 630,
640-641 (1981). Among those areas are ones where “the
interstate or international nature of the controversy
makes it inappropriate for state law to control.” Ibid. (citation omitted). In those areas, “the Constitution implicitly forbids” States from “apply[ing] their own law,” and
disputes in those inherently federal areas must “turn on
federal rules of law.” Franchise Tax Board v. Hyatt, 587
U.S. 230, 247 (2019) (internal quotation marks and citation
omitted). Put another way, “the basic scheme of the Constitution” “demands” a federal rule of decision in such inherently federal areas. American Electric Power Co. v.
Connecticut, 564 U.S. 410, 421 (2011).
When Congress has not created a rule of decision for
a particular question arising in an inherently federal area,
federal courts have the power to prescribe a rule as a matter of federal common law. See, e.g., Texas Industries,
451 U.S. at 640-641. Those court-created rules are subject
to displacement by statute, however, because “it is primarily the office of Congress, not the federal courts, to
prescribe national policy in areas of special federal interest.” American Electric Power, 564 U.S. at 423-424.
2. One established category of claims requiring a federal rule of decision is those seeking relief for injuries allegedly caused by interstate pollution. For more than a
century, “a mostly unbroken string of cases has applied
federal law to disputes involving” such claims. City of
New York, 993 F.3d at 91 (collecting cases). As this Court
has stated, federal law must govern such claims because
they “touch[] basic interests of federalism” and implicate
the “overriding federal interest in the need for a uniform
rule of decision.” Illinois v. City of Milwaukee (Milwaukee I), 406 U.S. 91, 105 n.6 (1972).
6
In the absence of an applicable federal statute, courts
previously applied federal common law to claims seeking
relief for interstate air and water pollution. See, e.g., Milwaukee I, 406 U.S. at 103; Georgia v. Tennessee Copper
Co., 206 U.S. 230, 237 (1907). But Congress later enacted
comprehensive legislation governing interstate air and
water pollution—the Clean Air Act and the Clean Water
Act.
This Court addressed the effect of the Clean Water
Act on the preexisting federal common law in City of Milwaukee v. Illinois (Milwaukee II), 451 U.S. 304 (1981).
There, the Court held that the Clean Water Act precluded
federal-common-law claims seeking to abate a nuisance
created by water pollution commencing in another State.
Id. at 317. Then, in International Paper Co. v. Ouellette,
479 U.S. 481 (1987), the Court addressed the role of state
law in the wake of the Clean Water Act’s enactment. The
Court held that, in light of the Clean Water Act’s “pervasive regulation” and “the fact that the control of interstate
pollution is primarily a matter of federal law,” the only
permissible state-law actions seeking relief for interstate
water pollution are “those specifically preserved by the
Act.” Id. at 492 (citation omitted). The Court then held
that the Clean Water Act preserved only suits under the
law of the State in which the source of pollution at issue
was located. See id. at 487-498.
In American Electric Power, supra, the Court addressed the effect of the Clean Air Act on the federal common law governing air pollution. The Court held that the
Act displaced nuisance claims under federal common law
seeking the abatement of greenhouse-gas emissions from
another State. See 564 U.S. at 424. The Court left open
the question whether “the law of each State where the defendants operate powerplants” could be applied. Id. at
429.
7
3. Another established category of claims requiring a
federal rule of decision is those that threaten to “impair
the effective exercise of the Nation’s foreign policy.”
Zschernig v. Miller, 389 U.S. 429, 440 (1968). As the
Court has explained, numerous constitutional and statutory provisions “reflect[] a concern for uniformity” and “a
desire to give matters of international significance to the
jurisdiction of federal institutions.” Banco Nacional de
Cuba v. Sabbatino, 376 U.S. 398, 427 n.25 (1964). The federal government accordingly has “exclusive authority in
international relations,” Fuld v. Palestine Liberation Organization, 145 S. Ct. 2090, 2104 (2025) (internal quotation marks and citation omitted), and “at some point an
exercise of state power that touches on foreign relations
must yield to the National Government’s policy,” American Insurance Association v. Garamendi, 539 U.S. 396,
413 (2003) (citation omitted).
B. Facts And Procedural History
1. Since 2017, state and local governments across the
country have filed lawsuits against private energy companies, alleging that the companies’ worldwide production,
promotion, and sale of fossil fuels have contributed to
global climate change and thereby caused injury. Nearly
60 state and local governments have brought such suits,
and more continue to be filed.
In 2021, the Second Circuit unanimously held in City
of New York that federal law precludes state-law claims
seeking relief for injuries allegedly caused by global climate change. The claims had to be brought under federal
common law, the court explained, but the Clean Air Act
displaced any such claims with respect to emissions in the
United States, and “foreign policy concerns foreclose[d]”
such claims with respect to international emissions. 993
8
F.3d at 101. The court rejected the notion that the displacement of federal common law allowed state-law claims
to proceed, except to the extent a plaintiff is seeking relief
for injuries caused by in-state emissions. See id. at 99100. But the plaintiff in City of New York was “not
seek[ing] to take advantage of this slim reservoir of state
common law.” Id. at 100. After the Second Circuit’s decision, the plaintiff did not seek this Court’s review.
Following that defeat in federal court, state and local
governments are now bringing these cases in state court.
Each case seeks billions of dollars in damages from the
defendant energy companies.
2. Petitioners in this case are leading energy companies; their primary business is the production and sale of
fossil fuels around the world. Respondents are the city of
Boulder, Colorado, and the surrounding county.
On April 17, 2018, respondents brought this case in
Colorado state court, alleging that petitioners’ worldwide
conduct has contributed to global climate change, which
in turn has caused a variety of harms in Colorado. Respondents allege that “unchecked production, promotion,
refining, marketing, and sale of fossil fuels” throughout
the world has “led to unchecked fossil fuel use,” resulting
in an “unprecedented rapid rise in the concentration of
[greenhouse gases] in the atmosphere.” Am. Compl. 2.
That increasing concentration of greenhouse gases, respondents allege, results in “warming [of] the atmosphere
and oceans” and “alteration of the climate,” including rising “global average temperatures.” Id. at 2, 30-33. According to respondents, the effects of climate change manifest in “increases in extreme hot summer days and increases in minimum nighttime temperatures, precipitation changes, larger and more frequent wildfires, increased concentrations of ground-level ozone, higher
transmission of viruses and disease from insects, altered
9
streamflows, bark beetle outbreaks, ecosystem damage,
forest die-off, reduced snowpack, and drought.” Id. at 3435.
Respondents asserted state-law claims for public nuisance; private nuisance; trespass; unjust enrichment; violation of the Colorado Consumer Protection Act, Colo.
Rev. Stat. § 6-1-105(1); and civil conspiracy. Am. Compl.
101-121. Each claim was premised on the same basic theory of liability: namely, that petitioners “altered the climate by selling fossil fuels at levels [it] knew would bring
numerous and catastrophic injuries to Colorado.” Resp.
Colo. S. Ct. Br. 1. Respondents sought to recoup past and
future projected climate-change costs from petitioners.
Am Compl. 1-2, 121-122.*
3. Petitioners removed this case to federal court, and
the district court granted a motion to remand. 405 F.
Supp. 3d 947 (D. Colo. 2019). On appeal, the Tenth Circuit
initially affirmed. 965 F.3d 792 (2020). After this Court’s
decision in BP p.l.c. v. Mayor & City Council of Baltimore, 141 S. Ct. 1532 (2021), the Court granted certiorari,
vacated the Tenth Circuit’s decision, and remanded for
further consideration of the jurisdictional question. 141 S.
Ct. 2667 (2021). The Tenth Circuit again affirmed. 25
F.4th 1238 (2022). Petitioners sought review from this
Court; the Court called for the views of the Solicitor General and then denied certiorari, with Justice Kavanaugh
dissenting. 143 S. Ct. 78 (2022); 143 S. Ct. 1795 (2023).
4. Petitioners then moved to dismiss the amended
complaint in state court, arguing in relevant part that federal law precludes state-law claims seeking relief for inju-
Respondents also asserted claims against Suncor Energy Inc.;
those claims were dismissed for lack of personal jurisdiction, and that
entity is not a party before this Court. See App., infra, 75a-87a.
*
10
ries allegedly caused by the effects of interstate greenhouse-gas emissions on the global climate. The district
court denied petitioners’ motion, holding that federal law
did not preclude respondents’ claims. App., infra, 87a115a.
5. Petitioner Exxon Mobil Corporation petitioned the
Colorado Supreme Court for interlocutory review; the
Suncor petitioners later joined in that request; and the
court granted review. App., infra, 7a. Following briefing
and oral argument, the court affirmed the district court’s
order by a 5-2 vote. Id. at 1a-47a.
a. The Colorado Supreme Court first concluded that,
because the Clean Air Act displaced the federal common
law that previously governed claims concerning interstate
air pollution, federal common law played no role in assessing whether federal law precludes respondents’
claims. App., infra, 9a-11a. The court acknowledged this
Court’s holding that federal common law governs disputes
concerning “interstate and international disputes implicating the conflicting rights of states or the United
States’s relations with foreign nations.” Id. at 9a (citing
American Electric Power, 564 U.S. at 421). But it reasoned that the Clean Air Act displaced the federal common law of nuisance, and it thus “look[ed] to whether the
[Clean Air Act] preempts [respondents’] claims.” Id. at
11a. The Colorado Supreme Court thereby expressly departed from the decisions in City of New York, supra, and
Illinois v. City of Milwaukee, 731 F.2d 403, 411 (7th Cir.
1984), in which federal courts of appeals held that the displacement of federal common law does not “resuscitate”
state-law claims. App., infra, 18a-20a.
The Colorado Supreme Court further concluded that
federal common law would not have applied even if it were
not displaced. App., infra, 18a. The court reasoned that
11
respondents have not “brought an action against a pollution emitter to abate pollution” and instead “seek[] damages from upstream producers for harms stemming from
the production and sale of fossil fuels.” Id. at 17a. The
court thus determined that respondents’ claims “do not
seek to regulate [greenhouse-gas] emissions.” Id. at 21a.
After reasoning that ordinary preemption analysis applied, the Colorado Supreme Court concluded that the
Clean Air Act did not alone preempt respondents’ claims.
App., infra, 11a-16a. Applying the presumption against
preemption, the court concluded that respondents’ claims
were not subject to either field preemption or conflict
preemption. Id. at 13a-15a.
Finally, the Colorado Supreme Court concluded that
respondents’ claims for injuries based on international
emissions could also proceed. App., infra, 22a-24a. Because the court determined that respondents’ claims “involve areas of traditional state responsibility” and do not
seek to regulate greenhouse-gas emissions, it held that respondents’ claims do not intrude on or conflict with any
federal power over foreign policy and are accordingly not
subject to foreign-affairs preemption. Id. at 24a.
b. Justice Samour, joined by Justice Boatright, dissented. App., infra, 25a-47a. In his view, the “majority
arrive[d] at the wrong result because it applie[d] the
wrong test.” Id. at 27a. Rather than applying “ordinary
statutory preemption,” Justice Samour contended that
“the appropriate inquiry with respect to the interstate aspect of [respondents’] claims is whether the [Clean Air
Act] affirmatively authorize[d] them,” which “it does not.”
Id. at 26a-27a. He rejected the majority’s position that
the presumption against preemption applied, explaining
that “Congress’s decision to displace federal common law
and to take control of this area did not suddenly render
12
state law competent to regulate interstate and international air pollution.” Id. at 26a. Justice Samour concluded
by “urg[ing] [this Court] to take up this issue,” “[g]iven
the number of local municipalities throughout the country
that have already brought claims like those advanced by
Boulder, given that more and more municipalities are
joining this trend, and given further that a number of
courts have now ruled that such claims may be prosecuted.” Id. at 46a.
6. The Colorado Supreme Court subsequently stayed
its mandate in order to allow petitioners to seek review in
this Court. App., infra, 140a-141a.
REASONS FOR GRANTING THE PETITION
This case presents a case-dispositive and recurring
question of extraordinary importance to the energy industry, which is facing dozens of lawsuits seeking billions of
dollars in damages for the alleged effects of global climate
change. That question is whether federal law precludes
the application of state law to claims seeking relief for injuries allegedly caused by interstate and international
greenhouse-gas emissions. By allowing respondents’
state-law claims to proceed, the Colorado Supreme
Court’s decision squarely conflicts with the Second Circuit’s decision in City of New York v. Chevron Corp., 993
F.3d 81 (2021), and is inconsistent with the decisions of
two other federal courts of appeals. The Colorado Supreme Court’s decision also conflicts with this Court’s
precedents: regulation of interstate pollution is an inherently federal area necessarily governed by federal law,
and Congress has not permitted, and indeed has preempted, resort to state law except for claims seeking relief for
harms caused by in-state emissions.
13
In these cases, state and local governments are attempting to assert control over the Nation’s energy policies by holding energy companies liable for worldwide
conduct in ways that starkly conflict with our constitutional structure, as well as the policies and priorities of the
federal government. That flouts the Court’s precedents
and basic principles of federalism. The petition for a writ
of certiorari should be granted. At a minimum, the Court
may wish to call for the views of the Solicitor General to
obtain the perspective of the new Administration.
A. The Decision Below Deepens A Conflict On The Question Presented And Is At Odds With The Views of the
United States
As the Colorado Supreme Court recognized, its decision squarely conflicts with the Second Circuit’s decision
in City of New York, which held that federal law precluded
materially identical state-law claims. The decision below
joins the Hawaii Supreme Court in a growing conflict, and
it is also inconsistent with decisions of the Fourth and Seventh Circuits. As a result of that conflict, trial courts
across the country are reaching divergent outcomes. This
Court’s review is warranted.
1. City of New York involved a suit brought by a municipal government against a group of energy companies
in federal court, alleging that the defendants (including
petitioner ExxonMobil) were liable for injuries allegedly
caused by the contribution of interstate and international
greenhouse-gas emissions to global climate change. As
here, the plaintiff municipality asserted claims for public
nuisance, private nuisance, and trespass, and sought relief
in the form of damages. See 993 F.3d at 88. As here, the
complaint alleged that the defendants had “known for
decades that their fossil fuel products pose a severe risk
to the planet’s climate” but had “downplayed the risks and
continued to sell massive quantities of fossil fuels, which
14
has caused and will continue to cause significant changes
to the * * * climate.” Id. at 86-87.
The question before the Second Circuit was “whether
municipalities may utilize state tort law to hold multinational oil companies liable for the damages caused by
global greenhouse gas emissions.” 993 F.3d at 85. The
court unanimously held that “the answer is ‘no.’ ” Id. at
85, 91.
The Second Circuit explained that, “[f]or over a century, a mostly unbroken string of cases has applied federal law to disputes involving interstate air or water pollution.” 993 F.3d at 91. “[S]uch quarrels,” the court continued, “often implicate two federal interests that are incompatible with the application of state law”: the “overriding need for a uniform rule of decision” on matters influencing national energy and environmental policy, and
“basic interests of federalism.” Id. at 91-92 (alterations
omitted) (quoting Illinois v. City of Milwaukee (Milwaukee I), 406 U.S. 91, 105 n.6 (1972)).
To the Second Circuit, claims seeking to hold defendants liable for injuries arising from “the cumulative impact of conduct occurring simultaneously across just
about every jurisdiction on the planet” are far too
“sprawling” for state law to govern. 993 F.3d at 92. The
court reasoned that application of state law to the plaintiff ’s claims would “risk upsetting the careful balance that
has been struck between the prevention of global warming, a project that necessarily requires national standards
and global participation, on the one hand, and energy production, economic growth, foreign policy, and national security, on the other.” Id. at 93.
The Second Circuit rejected the plaintiff ’s argument
that displacement by the Clean Air Act of any remedy under federal common law allows state law to govern. See
993 F.3d at 98. “[That] position is difficult to square with
15
the fact that federal common law governed this issue in
the first place,” the court reasoned, because “where ‘federal common law exists, it is because state law cannot be
used.’ ” Ibid. (quoting City of Milwaukee v. Illinois (Milwaukee II), 451 U.S. 304, 313 n.7 (1981)). The court thus
concluded that “state law does not suddenly become presumptively competent to address issues that demand a
unified federal standard simply because Congress saw fit
to displace a federal court-made standard with a legislative one.” Ibid. Such an outcome, the Second Circuit reasoned, is “too strange to seriously contemplate.” Id. at 9899.
The Second Circuit understood Congress to have the
power to “grant [S]tates the authority to operate in an
area of national concern,” but “resorting to state law on a
question previously governed by federal common law is
permissible only to the extent authorized by federal statute.” 993 F.3d at 99 (internal quotation marks, citations,
and alterations omitted). The court concluded that the
Clean Air Act “does not authorize the type of state-law
claims” the plaintiff was pursuing. Ibid. In the Second
Circuit’s view, the Act permitted only actions brought under “the law of the [pollution’s] source [S]tate,” and the
plaintiff was not proceeding under that “slim reservoir of
state common law.” Id. at 100 (first alteration in original)
(citation omitted).
The Second Circuit further explained that the Clean
Air Act did not displace federal common law with respect
to claims for harms caused by international emissions, because the Act “does not regulate foreign emissions.” 993
F.3d at 95 n.7, 101. But the court concluded that “condoning an extraterritorial nuisance action” for global climate
change “would not only risk jeopardizing our [N]ation’s
foreign policy goals but would also seem to circumvent
Congress’s own expectations and carefully balanced
16
scheme of international cooperation on a topic of global
concern.” Id. at 103.
2. The decision in City of New York squarely conflicts
with the Colorado Supreme Court’s decision in this case,
as well as the Hawaii Supreme Court’s decision in City &
County of Honolulu v. Sunoco LP, 537 P.3d 1173
(2023), cert. denied, 145 S. Ct. 1111 (2025). Each of those
cases involves tort claims asserted under state law seeking to hold fossil-fuel producers liable for injuries resulting from the cumulative effect of interstate and international greenhouse-gas emissions caused by the producers’
worldwide production, sale, and promotion of fossil fuels.
But unlike the Second Circuit, the Colorado Supreme
Court and the Hawaii Supreme Court held that such
claims could proceed under state law.
a. Like the Second Circuit, the Colorado Supreme
Court recognized that the Clean Air Act displaced any
“federal common law concerning air pollution.” App., infra, 10a. But the court proceeded to hold that, after that
displacement, state law was presumptively competent to
govern such actions concerning interstate and international pollution, unless the Clean Air Act demonstrated
Congress’s “clear and manifest purpose” to “supersede[]”
state law. Id. at 11a. The court acknowledged that the
Second Circuit had reached a contrary result, but it expressly declined to follow the Second Circuit’s decision,
criticizing that court’s analysis as “backwards reasoning.”
Id. at 19a (citation omitted).
Further disagreeing with the Second Circuit, the Colorado Supreme Court rejected the contention that claims
like respondents’ represent a de facto attempt to regulate
greenhouse-gas emissions. App., infra, 20a-21a. The
court instead distinguished between “claims against the
pollution emitters themselves,” which “implicat[e] the
regulation of interstate pollution,” and claims “seek[ing]
17
damages from upstream producers for harms stemming
from the production and sale of fossil fuels.” Id. at 17a.
The Second Circuit had rejected that distinction, explaining that “[a]rtful pleading cannot transform the [plaintiff’s] complaint into anything other than a suit over global
greenhouse gas emissions.” 993 F.3d at 91. In the Second
Circuit’s view, the plaintiff was seeking relief “precisely
because fossil fuels emit greenhouse gases” and thereby
exacerbate climate change, and it thus declined to allow
the plaintiff to “disavow[] any intent to address emissions”
while “identifying such emissions” as the source of its
harm. Ibid.
Because the Colorado Supreme Court determined
that respondents’ claims do not implicate a federal interest but instead “involve areas of traditional state responsibility,” it concluded that they do not conflict with any express foreign policy of the federal government or intrude
on any power over foreign policy reserved to the federal
government. App., infra, 23a-24a. By contrast, the Second Circuit had concluded that condoning materially similar claims “would not only risk jeopardizing our
[N]ation’s foreign policy goals but would also seem to circumvent Congress’s own expectations and carefully balanced scheme of international cooperation on a topic of
global concern.” 993 F.3d at 103.
b. Like the Colorado Supreme Court, the Hawaii Supreme Court held that state law was presumptively competent to govern actions concerning interstate and international pollution. See City & County of Honolulu, 537
P.3d at 1195-1202. The court reasoned that, because federal common law “no longer exists,” the fact that it once
governed could “play[] no part in th[e] court’s preemption
analysis.” Id. at 1199 (citation omitted). Instead, the
court concluded that the “correct preemption analysis requires an examination only of the [Clean Air Act]’s
18
preemptive effect.” Id. at 1200. The court acknowledged
that its decision conflicted with the Second Circuit’s,
which it said “rel[ied] on flawed reasoning.” Id. at 1196,
1200.
The Hawaii Supreme Court additionally concluded
that the plaintiffs’ claims did not arise in an inherently
federal area. See 537 F.3d at 1201. In the court’s view,
the inherently federal area of interstate pollution covers
only claims where “the source of the injury * * * is pollution traveling from one state to another.” Ibid. But the
claims before it, the court continued, concerned only “allegedly tortious marketing conduct.” Ibid. The court did
not attempt to reconcile that characterization with its earlier recognition that the plaintiffs’ theory of liability depended upon the defendant energy companies’ conduct allegedly “dr[iving] consumption [of fossil fuels], and thus
greenhouse gas pollution, and thus climate change,” resulting in alleged physical and economic effects in Honolulu. Id. at 1187 (citation omitted). The court also drew
no distinction between interstate and international emissions, holding that the plaintiffs’ state-law claims could
proceed as to both. See id. at 1195-1202. The Hawaii Supreme Court’s decision, like the Colorado Supreme
Court’s decision in this case, is thus hopelessly irreconcilable with the Second Circuit’s decision in City of New
York.
3. The decision below is also inconsistent with the decisions of two other federal courts of appeals that have
held that the law of one State cannot govern claims seeking relief for injuries emanating from pollution emitted in
another state.
a. In Illinois v. City of Milwaukee (Milwaukee III),
731 F.2d 403 (7th Cir. 1984), cert. denied, 469 U.S. 1196
(1985), the State of Illinois filed nuisance claims under
federal and state common law against a municipality for
19
allegedly polluting Lake Michigan. While the action was
pending, Congress enacted comprehensive amendments
to the Clean Water Act, and this Court held that those
amendments had displaced the remedy previously available under federal common law. See Milwaukee II, 451
U.S. at 317-319.
On remand, the Seventh Circuit addressed whether Illinois’s state-law claims could proceed in light of the displacement of federal common law. The Seventh Circuit
held that they could not. See 731 F.2d at 406. As the Seventh Circuit explained, this Court’s precedents provide
that “the basic interests of federalism and the federal interest in a uniform rule of decision in interstate pollution
disputes required the application of federal law.” Id. at
407. Although Congress had displaced the federal common law, the court reasoned that the displacement “did
nothing to undermine” the “reasons why the [S]tate
claiming injury cannot apply its own state law to out-ofstate discharges.” Id. at 410. The court thus held that
“federal law must govern * * * except to the extent
that the [Clean Water Act] authorizes resort to state law.”
Id. at 411. Because Congress had not preserved state-law
claims related to out-of-state sources, the Seventh Circuit
determined that federal law precluded Illinois’s claims.
See id. at 413.
b. The Fourth Circuit reached a similar result in
North Carolina ex rel. Cooper v. Tennessee Valley Authority, 615 F.3d 291 (2010). There, the State of North
Carolina sued the Tennessee Valley Authority (TVA) over
emissions from TVA plants in Alabama and Tennessee.
See id. at 296. The district court found that the emissions
created a public nuisance under North Carolina law and
entered an injunction in the State’s favor. See ibid.
20
The Fourth Circuit reversed. It reasoned that the
“comprehensive” system of federal statutes and regulations governing air pollution left little room for nuisance
actions under state law, and it concluded that North Carolina was improperly seeking to “appl[y] home state law
extraterritorially.” 615 F.3d at 296, 298. Applying this
Court’s decision in International Paper Co. v. Ouellette,
479 U.S. 481 (1987), the Fourth Circuit concluded that the
claims could proceed only under the law of the States in
which the TVA plants were located. See 615 F.3d at 308309; see also Merrick v. Diageo Americas Supply, Inc.,
805 F.3d 685, 692 (6th Cir. 2015) (agreeing that Ouellette’s
interpretation of the Clean Water Act’s saving clauses applies to the Clean Air Act’s saving clauses); Bell v. Cheswick Generating Station, 734 F.3d 188, 196-197 (3d Cir.
2013) (same), cert. denied, 572 U.S. 1149 (2014); Freeman
v. Grain Processing Corp., 848 N.W.2d 58, 80 (Iowa)
(same), cert. denied, 574 U.S. 1026 (2014); Brown-Forman Corp. v. Miller, 528 S.W.3d 886, 892-893 (Ky. 2017)
(same).
c. Both Milwaukee III and Cooper reflect the
broader principle that state law can govern claims seeking
relief for interstate pollution only to the extent permitted
by federal statute. Notably, the Colorado Supreme Court
explicitly rejected petitioners’ reliance on Milwaukee III,
concluding instead that, when federal common law is displaced by statute, a court should look only to whether the
statute affirmatively preempts state-law claims. App., infra, 20a.
4. The Colorado Supreme Court’s decision is also
contrary to the views of the United States. In an amicus
brief recently submitted to the Maryland Supreme Court,
the United States expressed the view that, “[u]nder our
constitutional system, regulation of interstate pollution
has always been primarily ‘a matter of federal, not state
21
law.’ ” U.S. Br. at 1, Mayor & City Council of Baltimore
v. BP p.l.c., No. 11, Sept. Term 2025 (Md.) (citation omitted). The United States thus argued that “[S]tates lack
authority to decide how much greenhouse gas emissions
in a neighboring state or foreign country are too much,”
and that “[a]ny attempt to do so would be preempted by
federal law.” Ibid.
The Administration has elsewhere made clear its view
that claims seeking relief from energy companies for the
effects of global climate change cannot proceed under
state law. In an executive order, the President has criticized these lawsuits for attempting to “regulate energy
beyond [the plaintiffs’] constitutional or statutory authorities,” which “undermine[s] [f]ederalism by projecting the
regulatory preferences of a few States into all States.”
Exec. Order No. 14,260 (Apr. 8, 2025). The United States
has gone so far as to sue the States of Hawaii and Michigan to prevent additional climate-change actions from being filed. See United States v. Michigan, Civ. No. 25-496
(W.D. Mich. Apr. 30, 2025); United States v. Hawaii, Civ.
No. 25-179 (D. Haw. Apr. 30, 2025).
This Administration may be more vocal than its predecessors, but the federal government’s disquiet with the
climate-change litigation is nothing new. In December
2024, the Biden Administration told the Court that the defendants in these suits “may ultimately prevail on their
contention that respondents’ claims are barred by the
Constitution.” U.S. Br. at 12, Sunoco LP v. City & County
of Honolulu, 145 S. Ct. 1111 (2025) (No. 23-947). And the
first Trump Administration argued that “[i]nterstate pollution claims” fall within “an inherently federal area in
which state law does not apply.” U.S. En Banc Br. at 4,
City of Oakland v. BP p.l.c., 969 F.3d 895 (9th Cir. 2020)
(No. 18-16663).
22
The Colorado Supreme Court’s decision thus not only
deepens an existing conflict, but is contrary to the position
of the United States. This Court’s review is badly needed
to resolve the conflict and to prevent dozens of climatechange cases from improperly barreling ahead in state
court.
B. The Decision Below Is Incorrect
Respondents seek to impose damages on petitioners
for injuries allegedly caused by the effect of interstate and
international greenhouse-gas emissions on global climate
change. As a result, respondents’ claims fall squarely
within the inherently federal areas of interstate pollution
and foreign affairs. The Constitution precludes those
claims from proceeding under state law. The Colorado
Supreme Court’s contrary holding was incorrect and conflicts with this Court’s precedents.
1. Although state law is presumptively competent to
govern a wide variety of issues in our federal system,
there are certain areas in which “our federal system does
not permit the controversy to be resolved under state
law.” Texas Industries, Inc. v. Radcliff Materials, Inc.,
451 U.S. 630, 641 (1981). In such areas, “there is no beginning assumption that concurrent regulation by the
State is a valid exercise of its police powers.” United
States v. Locke, 529 U.S. 89, 108 (2000); see Buckman Co.
v. Plaintiffs’ Legal Committee, 531 U.S. 341, 348 (2001).
For over a century, this Court has held that interstate
pollution is an inherently federal area necessarily governed by federal law. For example, in Ouellette, the Court
stated that “the regulation of interstate water pollution is
a matter of federal, not state, law.” 479 U.S. at 488 (citation omitted); see id. at 492. And in American Electric
Power Co. v. Connecticut, 564 U.S. 410 (2011), the Court
23
reiterated that “air and water in their ambient or interstate aspects” are “meet for federal law governance.” Id.
at 421, 422; see City of New York, 993 F.3d at 91 (citing
additional cases).
That rule emanates from “the Constitution’s structure
and the principles of sovereignty and comity it embraces.”
National Pork Producers Council v. Ross, 143 S. Ct. 1142,
1156 (2023) (internal quotation marks and citation omitted). As this Court has explained, each State’s “equal dignity and sovereignty” under the Constitution implies “certain constitutional limitations on the sovereignty of all of
its sister States.” Franchise Tax Board v. Hyatt, 587 U.S.
230, 245 (2019) (internal quotation marks, alterations, and
citation omitted); see Fuld v. Palestine Liberation Organization, 145 S. Ct. 2090, 2104 (2025). One such limitation
is that “[s]tate sovereign authority is bounded by the
States’ respective borders.” Fuld, 145 S. Ct. at 2104; see
Bonaparte v. Tax Court, 104 U.S. 592, 594 (1882); United
States v. Bevans, 16 U.S. (3 Wheat.) 336, 387 (1818). The
equality of the States “implicitly forbids” States from applying their own laws to resolve “disputes implicating
their conflicting rights.” Hyatt, 587 U.S. at 246 (alteration
and citations omitted).
Allowing the law of one State to govern disputes regarding pollution emanating from another would violate
the “cardinal” principle that “[e]ach [S]tate stands on the
same level with all the rest,” by permitting one State to
impose its law on another State and its citizens. Kansas
v. Colorado, 206 U.S. 46, 97 (1907). Federal law must govern such controversies because they “touch[] basic interests of federalism” and implicate the “overriding federal
interest in the need for a uniform rule of decision.” Milwaukee I, 406 U.S. at 105 n.6. And because “borrowing
the law of a particular State would be inappropriate” to
24
resolve such interstate disputes, federal law must govern.
American Electric Power, 564 U.S. at 422.
2. In the absence of federal legislation governing issues of interstate pollution, this Court held that rules developed by the federal courts—federal common law—
would govern lawsuits seeking relief for injuries allegedly
caused by interstate pollution. See, e.g., American Electric Power, 564 U.S. at 420-423; Milwaukee I, 406 U.S. at
103. But in the wake of the enactment of the Clean Air
Act and Clean Water Act, this Court held that Congress
has displaced any previously available causes of action under federal common law. See American Electric Power,
564 U.S. at 424; Milwaukee II, 451 U.S. at 313-314.
This Court’s decision in Ouellette explains the limited
role of state law after the displacement of federal common
law by a comprehensive statutory scheme in an inherently
federal area of regulation. There, the Court held that, in
light of the “pervasive regulation” of the Clean Water Act
and “the fact that the control of interstate pollution is primarily a matter of federal law,” the only permissible statelaw actions seeking relief for interstate water pollution
are “those specifically preserved by the Act.” 479 U.S. at
492 (citation omitted). The Court proceeded to conclude
that the Clean Water Act preempts claims under any
State’s law other than the law of the State in which the
source of the pollution was located. See id. at 487-498.
3. The foregoing precedents lead to a straightforward result here: federal law, including our constitutional
structure and the Clean Air Act, precludes respondents’
state-law claims seeking relief for interstate emissions.
Respondents’ theory of liability is that petitioners
have “caused billions of tons of excess CO2 emissions”
throughout the world by “producing, promoting, refining,
marketing and selling fossil fuels at levels that have
caused and continue to cause climate change.” Am.
25
Compl. 2, 87. Respondents are seeking “monetary relief
to compensate” for “past and future damages and costs to
mitigate the impacts of climate change,” including wildfires, pests, droughts, extreme heat, and flooding. Id. at
104, 121-122. The “gravamen” of respondents’ complaint,
see Kurns v. Railroad Friction Products Corp., 565 U.S.
625, 635 (2012) (citation omitted), is thus that petitioners’
conduct increased the global use of fossil fuels, resulting
in increased global greenhouse-gas emissions, which contributed to global climate change and resulted in localized
physical effects in Boulder, Colorado. See City of New
York, 993 F.3d at 91.
Those claims fall squarely within the principle that
federal law governs claims seeking relief for interstate air
and water pollution. Respondents allege that their injuries are caused by the interstate and international emissions of greenhouse gases over many decades. See Am.
Compl. 2. Respondents’ requested relief—including damages, see, e.g., Kurns, 565 U.S. at 637—would have the effect of remedying injuries allegedly caused by emissions
outside Colorado. Respondents are simply attempting to
recover by moving up one step in the causal chain and suing the fuel producers rather than the emitters themselves.
The congressional displacement of federal common
law does not open the door to state-law claims unless the
Clean Air Act permits them. And the Clean Air Act does
not permit state-law claims based on emissions emanating
from another State. Instead, the Act provides the Environmental Protection Agency with authority to regulate
greenhouse-gas emissions from stationary sources, see
American Electric Power, 564 U.S. at 424-425; 42 U.S.C.
7411(b), (d), and to set greenhouse-gas emissions standards for cars, trains, airplanes, and other equipment. See
42 U.S.C. 7521(a)(1)-(2), (a)(3)(E), 7547(a)(1), (a)(5), 7571
26
(a)(2)(A). Accordingly, in light of the breadth of the Clean
Air Act’s governance of greenhouse-gas emissions, respondents’ state-law claims would be foreclosed even if a
presumption against preemption applied. Contra App.,
infra, 11a-16a.
4. Respondents’ claims based on international emissions cannot proceed under state law either. The federal
government has “exclusive authority in international relations.” Fuld, 145 S. Ct. at 2104 (internal quotation
marks, alterations, and citation omitted). There is “no
question” that “at some point an exercise of state power
that touches on foreign relations must yield to the National Government’s policy.” American Insurance Association v. Garamendi, 539 U.S. 396, 413 (2003). State laws
must therefore “give way if they impair the effective exercise of the Nation’s foreign policy.” Zschernig v. Miller,
389 U.S. 429, 440 (1968).
Because respondents seek relief for climate-changerelated harms, international emissions—which dwarf domestic emissions—are the primary causal mechanism underlying their alleged injuries. Foreign-policy principles
thus preclude the application of state law to regulate international emissions. As the Second Circuit explained in
City of New York, holding fuel producers such as petitioners liable for such emissions would “affect the price and
production of fossil fuels abroad”; “bypass the various diplomatic channels that the United States uses to address
this issue”; override “the United States’ longstanding position” of “oppos[ing] the establishment of liability and
compensation schemes at the international level”; and
“sow confusion and needlessly complicate the nation’s foreign policy, while clearly infringing on the prerogatives of
the political branches.” 993 F.3d at 103 & n.11. Accordingly, respondents can no more seek relief under state law
27
for injuries allegedly caused by international emissions
than for those allegedly caused by interstate emissions.
5. In the decision below, the Colorado Supreme
Court fundamentally misunderstood both the ability of
state law to operate in inherently federal areas and the
nature of respondents’ theory of liability.
The central premise of the decision below is that, when
Congress enacts a statute that displaces federal common
law, state law presumptively governs the issues previously governed by federal common law. See App., infra,
20a. But that logic ignores the reason why federal common law governed in the first place. In cases that involve
“interstate and international disputes implicating the conflicting rights of States or our relations with foreign nations,” only federal law can apply, because “our federal
system does not permit the controversy to be resolved under state law” at all. Texas Industries, 451 U.S. at 641.
In other words, where federal common law applies, it is
precisely because “state law cannot be used.” Milwaukee
II, 451 U.S. at 313 n.7.
The displacement of federal common law by federal
statutory law does “nothing to undermine” the “reasons
why the [S]tate claiming injury cannot apply its own state
law to out-of-state discharges.” Milwaukee III, 731 F.2d
at 410. State law could not govern interstate and international emissions before Congress acted, and the application of state law to such claims remains inconsistent with
our constitutional structure after statutory displacement,
even if federal law provides no remedy for the particular
claim alleged. Were it otherwise, Congress’s decision to
address an inherently federal issue directly by statute, so
as to displace federal common-law remedies, would result
in state common-law remedies suddenly becoming available. As the Second Circuit put it, that result is “too
28
strange to seriously contemplate.” City of New York, 993
F.3d at 98-99.
The Colorado Supreme Court concluded that this
Court’s instructions for the remand in American Electric
Power supported its analysis. See App., infra, 10a-11a.
That is exactly backwards. After holding that the Clean
Air Act displaced any federal common-law claim seeking
abatement of defendants’ greenhouse-gas emissions, the
Court remanded for the lower courts to consider the
plaintiffs’ parallel claims brought under the law of the
state in which each defendant power plant was located.
American Electric Power, 564 U.S. at 429. In so doing,
the Court directed that, “[i]n light of [its] holding that the
Clean Air Act displaces federal common law, the availability vel non of a state lawsuit depends, inter alia, on the
preemptive effect of the federal Act.” Ibid. The Court
cited Ouellette for the proposition that “the Clean Water
Act does not preclude aggrieved individuals from bringing
a nuisance claim pursuant to the law of the source State.”
Ibid. (citation omitted).
Those instructions support petitioners’ position, not
respondents’. As explained above, see p. 24, this Court
held in Ouellette that, because the Clean Water Act is
comprehensive in nature and “control of interstate pollution is primarily a matter of federal law,” “the only state
suits that remain available are those specifically preserved by the Act”: namely, suits under the law of the
source State. 479 U.S. at 492. In American Electric
Power, the Court was thus directing the lower courts to
apply the same analysis as in Ouellette—the same analysis petitioners are advancing here.
The Colorado Supreme Court separately concluded
that respondents’ claims did not fall within the inherently
federal area of interstate pollution because respondents
have “not brought an action against a pollution emitter to
29
abate pollution” but instead “seek[] damages from upstream producers for harms stemming from the production and sale of fossil fuels.” App., infra, 17a. According
to the court, therefore, respondents’ claims “do not seek
to regulate [greenhouse-gas] emissions.” Id. at 21a. That
is a false dichotomy. While respondents’ theory of tort liability may attack upstream conduct, the source of injury
is most certainly interstate and international emissions.
As one judge has put it, “there is no hiding the obvious”
that climate-change claims such as respondents’ present
“a clash over regulating worldwide greenhouse gas emissions and slowing global climate change.” Minnesota v.
American Petroleum Institute, 63 F.4th 703, 717 (8th Cir.
2023) (Stras, J., concurring) (citation omitted), cert. denied, 144 S. Ct. 620 (2024).
The complaint is candid on this point. Respondents
repeatedly allege that defendants’ conduct led to increased greenhouse-gas emissions worldwide, which
caused or exacerbated global climate change and thereby
caused localized harms in Colorado. See Am. Compl. 1-4,
30. Respondents nowhere allege harm from petitioners’
conduct other than through the mechanisms of increased
emissions and global climate change. When faced with the
same argument, the Second Circuit rightly held that a
plaintiff cannot “have it both ways” by “disavowing any
intent to address emissions” while simultaneously “identifying such emissions as the singular source of the [alleged] harm.” City of New York, 993 F.3d at 91.
The Colorado Supreme Court also erred by concluding
that respondents’ claims based on international emissions
could proceed. The federal government has “exclusive authority in international relations and with respect to foreign intercourse and trade.” Fuld, 145 S. Ct. at 2104 (internal quotation marks, alterations, and citation omitted).
The court disregarded that principle and, in so doing,
30
“risk[ed] impeding our federal government’s judgment as
to how to approach air pollution in the international
sphere.” App., infra, 45a (Samour, J., dissenting). The
Colorado Supreme Court erred by holding that respondents’ claims, seeking relief for interstate and international
greenhouse-gas emissions, could proceed under Colorado
law.
The decision below paves the way for “all other Colorado municipalities” to bring such claims. App., infra, 25a
(Samour, J., dissenting). Allowing those claims to proceed
under state law will result in a “patchwork of standards
formulated by local governments throughout the country”
that is “not capable of effectively addressing interstate air
pollution.” Id. at 45a.
C. The Question Presented Is Important And Warrants
The Court’s Review In This Case
This case presents a question of enormous legal and
practical importance. The decision below perpetuates an
unsustainable and chaotic patchwork of regulation of interstate and international emissions. And in doing so, it
threatens one of this Nation’s most critical industries.
This case is an excellent vehicle to review the question
presented in this case. The Court should therefore grant
review.
1. The stakes in this case could not be higher. The
Colorado Supreme Court itself explained that “this case
presents substantial issues of global import.” App., infra,
1a. And this is just one of over two dozen pending climatetort cases brought by States and municipalities across the
country seeking to impose untold damages on energy
companies for the physical and economic effects of climate
change. As more time passes, more governments are filing cases of their own. See, e.g., Hawaii v. BP p.l.c., No.
1CCV-25-717 (Haw. Cir. Ct. May 1, 2025); Maine v. BP
31
p.l.c., No. PORSC-CV-24-442 (Me. Super. Ct. Nov. 26,
2024). Individuals are now bringing their own cases. See
Leon v. Exxon Mobil Corp., No. 25-2-15986-8 (Wash. Super. Ct. May 29, 2025). And state legislatures are passing
laws to create so-called “climate superfunds” based on the
same theory of liability as the tort cases. See United
States v. New York, Civ. No. 25-3656 (S.D.N.Y. May 1,
2025) (challenging New York’s Climate Change Superfund Act); Chamber of Commerce v. Moore, Civ. No. 241513 (D. Vt. Dec. 30, 2024) (challenging Vermont’s Climate Superfund Act).
This is complete chaos. And without this Court’s intervention, the Nation will be left with a “patchwork of
standards formulated by local governments throughout
the country to regulate [greenhouse-gas] emissions,”
which will invite further disorder and will “not [be] capable of effectively addressing interstate air pollution.”
App., infra, 45a (Samour, J., dissenting). As the federal
government explained in its brief in American Electric
Power, “virtually every person, organization, company, or
government across the globe * * * emits greenhouse
gases, and virtually everyone will also sustain climatechange-related injuries,” giving rise to claims from “almost unimaginably broad categories of both potential
plaintiffs and potential defendants.” TVA Br. at 11, 15
(No. 10-174).
The use of state law to address global climate change
represents a serious threat to one of our Nation’s most
critical sectors. The current Administration has made
clear that “American energy dominance is threatened
when State and local governments seek to regulate energy beyond their constitutional and statutory authorities,” and that the climate-change litigation in particular
“weaken[s] our national security and devastate[s] Americans by driving up energy costs for families.” Exec. Order
32
No. 14,260. The Administration has even gone so far as to
sue States contemplating filing additional actions. See
United States v. Michigan, supra; United States v. Hawaii, supra; United States v. New York, supra. Indeed,
as the federal government previously stated in another
climate-change case, “federal law and policy has long declared that fossil fuels are strategically important domestic resources that should be developed to reduce the growing dependence of the United States on politically and economically unstable sources of foreign oil imports.” U.S.
En Banc Br. at 10, City of Oakland, supra (internal quotation marks and citation omitted).
2. This case is a suitable vehicle for reviewing the
question presented. The question was fully briefed in, and
passed on by, the Colorado Supreme Court. And respondents’ claims are representative of the claims being
brought in parallel suits across the country, meaning that
resolution of the question presented here will have immediate impact elsewhere.
Although this petition arises from a decision affirming
the denial of a motion to dismiss in State court, this
Court’s jurisdiction over the decision is firmly established
under 28 U.S.C. 1257(a) and the fourth category recognized in Cox Broadcasting Corp. v. Cohn, 420 U.S. 469
(1975). The question presented has been finally decided
by the Colorado Supreme Court; this Court’s review of
the question would be prevented if petitioners prevail on
the merits on nonfederal grounds; reversal of the decision
below would terminate the litigation; and declining review
now would seriously erode significant federal policies, as
evidenced by the current Administration’s stance on the
climate litigation. See Cox Broadcasting, 420 U.S. at 482483. This Court has routinely granted certiorari in a similar posture in cases presenting questions of federal preemption. See, e.g., Coventry Health Care of Missouri,
33
Inc. v. Nevils, 581 U.S. 87, 92-94 (2017); Dan’s City Used
Cars, Inc. v. Pelkey, 569 U.S. 251, 259 (2013); Mississippi
Power & Light Co. v. Mississippi ex rel. Moore, 487 U.S.
354, 370 n.11 (1988).
This Court’s guidance is urgently needed. The arguments on both sides of the question presented have been
fully ventilated in lower-court opinions, including the dueling opinions below. Meanwhile, state courts and parties
are devoting enormous resources to the litigation of these
cases, and the energy industry is facing the threat of damages awards that could run into the billions of dollars. The
Court should grant certiorari here and resolve whether
climate-change claims are viable and may proceed on the
merits in state courts across the country. At a minimum,
in light of the substantial federal interest in the question
presented and the change in Administration since the
Court last considered the question presented, the Court
may wish to call for the views of the Solicitor General.
34
CONCLUSION
The petition for a writ of certiorari should be granted.
Respectfully submitted.
HUGH QUAN GOTTSCHALK
ERIC L. ROBERTSON
WHEELER TRIGG
O’DONNELL LLP
370 Seventeenth Street,
Suite 4500
Denver, CO 80202
Counsel for Petitioners
Suncor Energy (U.S.A.) Inc.
and Suncor Energy Sales Inc.
KANNON K. SHANMUGAM
WILLIAM T. MARKS
JAKE L. KRAMER
EMMA R. WHITE
PAUL, WEISS, RIFKIND,
WHARTON & GARRISON LLP
2001 K Street, N.W.
Washington, DC 20006
(202) 223-7300
kshanmugam@paulweiss.com
THEODORE V. WELLS, JR.
DANIEL J. TOAL
YAHONNES CLEARY
PAUL, WEISS, RIFKIND,
WHARTON & GARRISON LLP
1285 Avenue of the Americas
New York, NY 10019
Counsel for Petitioner
Exxon Mobil Corporation
AUGUST 2025
This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.