Reply Brief — Suncor Energy (U.S.A.) Inc., et al., Petitioners v. County Commissioners of Boulder County, et al.

No. 25-170

In the Supreme Court of the United States

SUNCOR ENERGY (U.S.A.) INC., ET AL., PETITIONERS

v.

COUNTY COMMISSIONERS OF BOULDER COUNTY, ET AL.

ON WRIT OF CERTIORARI

TO THE SUPREME COURT OF COLORADO

REPLY BRIEF FOR THE PETITIONERS

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

JAKE L. KRAMER

ELEANOR K. RITTER

KEITH E. ZIMMERMAN

DAVIS POLK & WARDWELL LLP

1050 17th Street, N.W.

Washington, DC 20036

(202) 962-7000

kshanmugam@davispolk.com

TABLE OF CONTENTS

Page

I.

The Court has statutory and constitutional

jurisdiction over this case ............................................... 3

A. The Court has jurisdiction

under 28 U.S.C. 1257(a) ............................................ 3

B. The Court has jurisdiction

under Article III of the Constitution ...................... 5

II. The Constitution precludes state-law claims

seeking relief for injuries allegedly caused

by interstate greenhouse-gas emissions ....................... 7

A. The structure of the Constitution does not

allow the law of a single State to govern

claims concerning interstate emissions .................. 7

B. The Constitution does not allow States

to apply their law extraterritorially to reach

claims for injuries from global climate change ... 13

III. The Constitution precludes state-law claims

seeking relief for injuries allegedly caused

by international greenhouse-gas emissions ............... 18

IV. The Clean Air Act preempts state-law claims

seeking relief for injuries allegedly caused

by emissions from another State ................................. 19

TABLE OF AUTHORITIES

Cases:

American Electric Power Co. v. Connecticut,

564 U.S. 410 (2011) ................................... 2, 8-11, 17, 20-21

American Insurance Association v. Garamendi,

539 U.S. 396 (2003) ............................................................19

American Trucking Associations v. City of Los Angeles, 569 U.S. 641 (2013) .................................................21

ASARCO Inc. v. Kadish, 490 U.S. 605 (1989) ......................6

Atlantic Richfield Co. v. Christian,

590 U.S. 1 (2020) ..............................................................3, 4

(I)

II

Page

Cases—continued:

Atlantic Richfield Co. v. Montana Second Judicial

District Court, 408 P.3d 515 (Mont. 2017) .......................4

Bell v. Cheswick Generating Station,

734 F.3d 188 (3d Cir. 2013),

cert. denied, 572 U.S. 1149 (2014) ...................................21

Cameron v. District Court, 565 P.2d 925 (Colo. 1977) ........4

Camreta v. Greene, 563 U.S. 692 (2011) ................................5

City of Milwaukee v. Illinois, 451 U.S. 304 (1981) ..............2

Cox Broadcasting Corp. v. Cohn,

420 U.S. 469 (1975) .......................................................... 3-5

Diamond v. Charles, 476 U.S. 54 (1986) ...............................6

Edgar v. MITE Corp., 457 U.S. 624 (1982) .........................17

Fuld v. Palestine Liberation Organization,

606 U.S. 1 (2025) ................................................................14

Georgia v. Tennessee Copper Co.,

206 U.S. 230 (1907) ..............................................................7

Hillside Dairy Inc. v. Lyons, 539 U.S. 59 (2003) ................9

Illinois v. City of Milwaukee, 406 U.S. 91 (1972) ................9

Illinois v. City of Milwaukee,

731 F.2d 403 (7th Cir. 1984),

cert. denied, 469 U.S. 1196 (1985) ...................................14

International Paper Co. v. Ouellette,

479 U.S. 481 (1987) ..................................... 9, 11, 12, 17, 20

Kurns v. Railroad Friction Products Corp.,

565 U.S. 625 (2012) ............................................................13

Lamps Plus, Inc. v. Varela, 587 U.S. 176 (2019) .................6

M’Culloch v. Maryland,

17 U.S. (4 Wheat.) 316 (1819) ............................................7

Maine v. Taylor, 477 U.S. 131 (1986) ....................................5

Murphy v. National Collegiate Athletic

Association, 584 U.S. 453 (2018).......................................5

National Pork Producers Council v. Ross,

598 U.S. 356 (2023) ............................................... 14, 17, 18

New York Life Insurance Co. v. Head,

234 U.S. 149 (1914) ............................................................16

III

Page

Cases—continued:

Osborn v. Bank of the United States,

22 U.S. (9 Wheat.) 738 (1824) ............................................7

Pacific Gas & Electric Co. v. State Energy

Resources Conservation & Development

Commission, 461 U.S. 190 (1983) ...................................20

Pennoyer v. Neff, 95 U.S. 714 (1877) ...................................13

Phillips Petroleum Co. v. Shutts,

472 U.S. 797 (1985) ............................................................16

Prudential Insurance Co. v. Benjamin,

328 U.S. 408 (1946) ..............................................................9

Puerto Rico Department of Consumer Affairs

v. Isla Petroleum Corp., 485 U.S. 495 (1988) ..........12, 20

Puerto Rico v. Franklin California Tax-Free Trust,

579 U.S. 115 (2016) ............................................................12

Public Service Co. v. Van Wyk,

27 P.3d 377 (Colo. 2001) ...................................................21

Riegel v. Medtronic, Inc., 552 U.S. 312 (2008) ...................12

Seila Law LLC v. Consumer Financial Protection

Bureau, 591 U.S. 197 (2020) ..............................................6

South-Central Timber Development, Inc.

v. Wunnicke, 467 U.S. 82 (1984) .................................9, 11

Southern Pacific Co. v. Arizona ex rel. Sullivan,

325 U.S. 761 (1945) ..............................................................9

State v. Lord, 16 N.H. 357 (1844) .........................................15

Steel Co. v. Citizens for a Better Environment,

523 U.S. 83 (1998) ................................................................6

Stillman v. White Rock Manufacturing Co.,

23 F. Cas. 83 (C.C.D.R.I. 1847) .......................................15

Strassheim v. Daily, 221 U.S. 280 (1911) .....................14, 17

United States v. Pink, 315 U.S. 203 (1942) .........................19

United States v. Standard Oil Co.,

332 U.S. 301 (1947) ..............................................................8

Virginia Uranium, Inc. v. Warren,

587 U.S. 761 (2019) ............................................................20

Young v. Masci, 289 U.S. 253 (1933) ...................................14

Zschernig v. Miller, 389 U.S. 429 (1968) .............................19

IV

Page

Constitution, statutes, and rules:

U.S. Const.:

Art. I, § 8, cl. 3 .............................................................16, 17

Art. III..............................................................................5, 6

Art. IV, § 1 ...................................................................16, 17

Amend. XIV, § 1 ................................................................16

Clean Air Act, 42 U.S.C. 7401-7675 ............... 3, 10, 11, 19-21

42 U.S.C. 7410(a)(2)(D) ....................................................20

42 U.S.C. 7410(a)(2)(D)(i) ................................................21

42 U.S.C. 7411(c) ...............................................................21

42 U.S.C. 7416 ...................................................................21

42 U.S.C. 7545(o)(2)(A)(i) .................................................20

Clean Water Act, 33 U.S.C. 1251-1389 ................................11

28 U.S.C. 1257(a) ......................................................................3

28 U.S.C. 1292(b) ......................................................................6

Fed. R. Civ. P. 23(f)..................................................................6

Colo. App. R.:

Rule 4.2(a) ............................................................................4

Rule 4.2(h) ............................................................................4

Rule 21(a)(1) ........................................................................4

Rule 21(o) .............................................................................4

Rule 21 cmt. to 2024 amend. ..............................................4

Miscellaneous:

91 Fed. Reg. 7686 (Feb. 18, 2026) ........................................19

Joseph Story, Commentaries on the Conflicts of

Laws (5th ed. 1857)............................................................13

In the Supreme Court of the United States

No. 25-170

SUNCOR ENERGY (U.S.A.) INC., ET AL., PETITIONERS

v.

COUNTY COMMISSIONERS OF BOULDER COUNTY, ET AL.

ON WRIT OF CERTIORARI

TO THE SUPREME COURT OF COLORADO

REPLY BRIEF FOR THE PETITIONERS

Respondents do not dispute that, whatever the cause

of action, all of their claims share the same underlying

theory: that the global conduct of selected energy companies increased the global use of fossil fuels, which resulted

in increased greenhouse-gas emissions, which, when

mixed with emissions from billions of other global sources

over many decades, contributed to global climate change

and resulted in global harms. Respondents do not dispute

that this lawsuit is one of a coordinated series of similar

lawsuits—nearly 60, at last count—by state and local governments around the country. Respondents do not dispute that, on their theory, any state, city, or even individual in the country could bring similar claims. And respondents do not dispute that the intended effect of these

lawsuits is to impose an enormous “carbon tax,” in the

form of billions of dollars of damages, that could “bankrupt” the energy industry.

(1)

2

For those reasons, this litigation is unlike any other in

American history—with climate-change advocates seeking to bypass the political process and achieve sweeping

policy objectives through state-law causes of action

against arbitrary groups of defendants in handpicked forums. But while the litigation may be novel, the principles

barring the claims are not. In a self-contained proceeding, the Colorado Supreme Court definitively held that

federal law does not preempt respondents’ claims. That

holding was erroneous.

Two distinct but related constitutional principles bar

respondents’ claims. First, the Constitution’s structure

bars the application of state law to certain inherently federal areas, including interstate-pollution disputes. Citing

“the basic scheme of the Constitution,” this Court has

unanimously held that it would be “inappropriate” to apply “the law of a particular state” to resolve climatechange claims against the emitters of greenhouse gases.

American Electric Power Co. v. Connecticut, 564 U.S.

410, 421-422 (2011). It would be illogical to permit claims

to go forward against the producers of fossil fuels, which

stand further removed in the causal chain. And it would

be nonsensical to hold that state law can apply in areas in

which this Court has recognized that “state law cannot be

used,” City of Milwaukee v. Illinois, 451 U.S. 304, 313 n.7

(1981), simply because, as respondents argue, Congress

chose to displace federal common law with a federal statute.

Second, the Constitution’s prohibition on extraterritorial regulation independently precludes a State from extending its law beyond its borders to regulate global conduct with undifferentiated global effects. Respondents

seemingly embrace the breathtaking position that a State

can extraterritorially apply its law to conduct in another

State whenever the effects of the conduct are felt within

3

that State—no matter how tenuous the connection between the defendant’s conduct and the in-state effects.

That cannot be the law in our federalist system.

The problems with respondents’ claims do not stop

there. The use of state law to regulate global climate

change would also infringe on the exclusive role of the

President and Congress in foreign affairs. And far from

authorizing the application of state law, the Clean Air Act

independently preempts any effort by one State to impose

its law on emissions nationwide.

Whether independently or collectively, these principles foreclose respondents’ unprecedented use of state

law to address a global issue. A Boulder jury should not

be allowed to make national and international energy policy. The Colorado Supreme Court erred by permitting respondents’ claims to go forward, and its judgment should

be reversed.

I.

THE COURT HAS STATUTORY AND CONSTITUTIONAL JURISDICTION OVER THIS CASE

A. The Court Has Jurisdiction Under 28 U.S.C. 1257(a)

The Court has statutory jurisdiction both because this

case arises from a final determination of the Colorado Supreme Court in a self-contained original proceeding, and

because it falls within the fourth category of cases identified in Cox Broadcasting Corp. v. Cohn, 420 U.S. 469

(1975).

1. As to the first ground for statutory jurisdiction:

Atlantic Richfield Co. v. Christian, 590 U.S. 1 (2020), is

directly on point. Respondents primarily argue (Br. 1819) that Atlantic Richfield does not apply here because

petitioners asked the Colorado Supreme Court to “review

and reverse” the trial court’s decision, and the Colorado

Supreme Court ultimately remanded. But the very same

4

was true in Atlantic Richfield. See 408 P.3d 515, 518, 523

(Mont. 2017).

Respondents contend (Br. 16-18) that the relevant distinction is between the exercise of “original” and “appellate” jurisdiction. But Atlantic Richfield makes clear that

the correct inquiry is not whether the decision under review resembles an appeal in the sense that it reviewed the

substance of a lower-court decision, but rather whether

the proceeding was discrete from the underlying lawsuit

and thus “a self-contained case” under state law, such that

the ensuing decision is final for purposes of this Court’s

review. See 590 U.S. at 12. And to the extent that the

Colorado Supreme Court was exercising its “general superintending control” over the trial court (Br. 19-20), Colorado law establishes that it was still exercising original

jurisdiction, as distinct from ordinary appellate review.

See, e.g., Cameron v. District Court, 565 P.2d 925, 928

(Colo. 1977); Colo. App. R. 21(a)(1) & cmt. to 2024 amend.

Like other States, Colorado has separate procedures for

self-contained original proceedings and direct interlocutory appeals. See Colo. App. R. 4.2(a), (h).

Respondents are left to invent a rule that state-court

proceedings qualify as final under Atlantic Richfield only

when parties “seek writs against the trial court.” Br. 22.

But nothing in Atlantic Richfield suggests that limitation;

again, the relevant inquiry is simply whether the proceeding is “a self-contained case” distinct from the underlying

litigation. 590 U.S. at 12; see Former State Supreme

Court Justices Br. 5-6. Regardless, the trial court here

was a direct object of the order to show cause, which

would have been made “absolute” if petitioners had prevailed. J.A. 141-142; see Colo. App. R. 21(o).

2. As to the second ground for statutory jurisdiction:

the fourth Cox category requires only a showing that a

federal issue has been definitively resolved and that the

5

petitioner “might prevail on the merits on nonfederal

grounds,” such that future review of the federal issue

would be “unnecessary.” 420 U.S. at 482 (emphases

added). That is the case here. Reversal on the federal

issue would end the litigation, because respondents have

not asserted claims here based on “source-state law” or

“in-state emissions.” Br. 15. And delayed review would

expose one of this Nation’s most critical industries to untold liability, which is more than enough to threaten a serious erosion of federal policy. See U.S. Br. 3-4, 27-28.

Effectively acknowledging the fourth category’s applicability here, respondents assert (Br. 16) that the Court

should overrule Cox, but they offer no justification for

that drastic step.

B. The Court Has Jurisdiction Under Article III Of The

Constitution

The Court has constitutional jurisdiction because petitioners plainly have Article III standing. Respondents’

suggestion (Br. 11-14) that petitioners lack a personal

stake in the dispute sufficient to confer standing lacks

merit.

1. Most obviously, petitioners suffered an Article III

injury because the decision below definitively and adversely adjudicated their legal rights: specifically, their

federal preemption defense, with the result that petitioners have lost their “right[s] to engage in certain conduct”

“free from [state-law] requirements.” Murphy v. National Collegiate Athletic Association, 584 U.S. 453, 479

(2018). If the decision below is “left undisturbed,” petitioners “will be bound by the conclusive adjudication” of

that defense and face an increased risk of liability, not

only in this case but in other pending and future cases in

Colorado. Maine v. Taylor, 477 U.S. 131, 136 (1986); cf.

Camreta v. Greene, 563 U.S. 692, 702-703 (2011). The

6

mere fact that petitioners may eventually be able to defeat

liability on other grounds in this case does not eliminate

their stake in the dispute, any more than the prospect of

further proceedings did in ASARCO Inc. v. Kadish, 490

U.S. 605 (1989), in the face of a similarly definitive (but

interlocutory) “adjudication of [federal] legal rights.” Id.

at 618; see id. at 611-612. Indeed, respondents’ rule would

jeopardize Article III standing to appeal a wide array of

interlocutory orders commonly reviewed by appellate

courts. See, e.g., 28 U.S.C. 1292(b); Fed. R. Civ. P. 23(f).

2. Petitioners also suffered an Article III injury because they are subject to the burden of having to continue

defending against respondents’ claims. Monetary consequences flowing from an adverse decision constitute a

cognizable injury-in-fact. See Pet. Br. 20; U.S. Br. 14. Diamond v. Charles, 476 U.S. 54 (1986), is not to the contrary; it reflects the unremarkable proposition that a

party “cannot achieve standing to litigate a substantive issue by bringing suit for the cost of bringing suit.” Steel

Co. v. Citizens for a Better Environment, 523 U.S. 83, 107

(1998). Here, by contrast, the decision below will force petitioners to incur ongoing monetary costs involuntarily.

See Seila Law LLC v. Consumer Financial Protection

Bureau, 591 U.S. 197, 211 (2020). Petitioners’ “interest in

avoiding [adverse] consequences” of the decision below

gives them the “necessary personal stake in the appeal”

for Article III purposes. Lamps Plus, Inc. v. Varela, 587

U.S. 176, 182 (2019) (citation omitted).

7

II. THE CONSTITUTION PRECLUDES STATE-LAW

CLAIMS SEEKING RELIEF FOR INJURIES ALLEGEDLY CAUSED BY INTERSTATE GREENHOUSE-GAS

EMISSIONS

Two independent constitutional principles bar statelaw claims seeking relief for global climate change. First,

under the principle of equal sovereignty, the Constitution

limits the powers that the States previously enjoyed as independent sovereigns, with the result that States cannot

apply their laws in certain areas, including interstate pollution. Second, under the principle of extraterritoriality,

a State cannot extend its law to regulate conduct beyond

its borders, such as conduct causing global climate

change.

A. The Structure Of The Constitution Does Not Allow

The Law Of A Single State To Govern Claims Concerning Interstate Emissions

The plan of the Convention required the States to surrender certain preexisting powers in order to ensure each

State’s equal sovereignty. See Pet. Br. 22-24; Alabama

Br. 3-11, 15-16. Among those powers was the “forcible

abatement of outside nuisances,” such as air pollution

from neighboring States. Georgia v. Tennessee Copper

Co., 206 U.S. 230, 237 (1907). (Another was the ability to

conduct an independent foreign policy. See pp. 18-19, infra.) There can be no serious dispute that such a structural constitutional principle can have preclusive effect.

See, e.g., Osborn v. Bank of the United States, 22 U.S. (9

Wheat.) 738, 865 (1824); M’Culloch v. Maryland, 17 U.S.

(4 Wheat) 316, 430-431 (1819). And based on that constitutional principle, this Court has long held that federal

law necessarily and exclusively governs interstate-pollution claims, precisely because such claims implicate the

conflicting rights of States over a shared natural resource.

See Pet. Br. 26-27.

8

Respondents seemingly recognize (Br. 29) that the

Constitution precludes applying state law to at least some

interstate-pollution disputes. Respondents instead quibble (Br. 31-33) that the former federal common law of interstate pollution would not have covered their claims.

Respondents further suggest (Br. 30) that, if the Constitution bars applying state law, it would be impossible for

Congress to provide otherwise. And respondents insist

(Br. 43-45) that, once Congress displaced the former federal common law of interstate air pollution, state law can

operate unless Congress affirmatively preempts it. Each

of those contentions lacks merit.

1. With regard to the scope of the former federal

common law, respondents seemingly contend that, because the federal common law would not have provided a

cause of action in these circumstances, the Constitution

does not preclude a state-law claim. But that contention

rests on the false premise that the scope of the available

cause of action under the former federal common law defines the scope of what is constitutionally committed to

federal law. The application of federal common law to interstate-pollution disputes was a manifestation of the constitutional principle of equal sovereignty. A federal court,

exercising its authority to fashion common law, can decline to allow certain litigants to “invoke” a common-law

cause of action. American Electric Power, 564 U.S. at

422; see, e.g., United States v. Standard Oil Co., 332 U.S.

301, 308, 314 (1947). But that does not make such claims

any less “meet for federal law governance.” American

Electric Power, 564 U.S. at 422.

In any event, there is no merit to respondents’ contention that the cause of action under federal common law

was limited to “suits brought by one State to abate pollution emanating from another State.” Br. 31-32 (citation

omitted). As this Court has explained, “[w]hen we deal

9

with air and water in their ambient or interstate aspects,

there is a federal common law.” American Electric

Power, 564 U.S. at 421 (citation omitted). The interstate

conflict hardly dissolves simply because a suit is being

brought by a municipality rather than a State; in both instances, one State’s law is applied to regulate an inherently federal area. See Illinois v. City of Milwaukee, 406

U.S. 91, 105 n.6 (1972). The same “overriding federal interest in the need for a uniform rule of decision” and

“basic interests of federalism” exist. Ibid. And that is also

true regardless of the form of relief sought. Cf. International Paper Co. v. Ouellette, 479 U.S. 481, 498 n.19 (1987).

2. With regard to Congress’s power to authorize the

application of state law, the Court has previously called

respondents’ view “altogether fallacious,” because it

equates the “implied prohibition” of state law with the “affirmative endowment” of congressional authority. Prudential Insurance Co. v. Benjamin, 328 U.S. 408 (1946).

“Congress certainly has the power to authorize regulations that burden or discriminate against interstate commerce,” Hillside Dairy Inc. v. Lyons, 539 U.S. 59, 66

(2003), including in ways that would “otherwise not be

permissible” if done by the States themselves, Southern

Pacific Co. v. Arizona ex rel. Sullivan, 325 U.S. 761, 769

(1945). In this context, that makes good sense: any violation of a State’s sovereignty is ameliorated when Congress acts, because “all segments of the country are represented[] and there is significantly less danger that one

State will be in a position to exploit others.” South-Central Timber Development, Inc. v. Wunnicke, 467 U.S. 82,

92 (1984).

In a related vein, respondents suggest (Br. 30-31) that,

because petitioners have acknowledged that the law of the

source State can apply in other contexts, petitioners have

10

somehow conceded the question presented. That is a gimmicky claim. The fact that Congress has authorized the

application of source-state law to a bilateral interstatepollution dispute does not imply the broader authority to

apply state law to a claim seeking redress for global climate change. Respondents conspicuously do not contend

that Congress has authorized state law to apply to the latter type of claims. Indeed, those claims would be unlike

anything Congress has ever authorized and would constitute a remarkable abdication of its authority over the Nation’s foreign policy.

3. With regard to displacement, when Congress enacted the Clean Air Act, it displaced the former federal

common law of interstate pollution (but notably did not

displace federal common law as to claims based on international emissions). To the extent respondents contend

that Congress was required affirmatively to preempt

state law as to interstate emissions, that contention lacks

merit.

a. To begin with, respondents’ position is illogical.

Despite respondents’ feeble efforts to suggest otherwise,

see pp. 14-15, infra, plaintiffs could not bring interstatepollution claims under the affected State’s law before the

enactment of the Clean Air Act. The upshot of respondents’ position, then, is that state law could spring into life

after the Clean Air Act displaced the former federal common law of interstate pollution, even though Congress did

not authorize the application of state law. But the reason

federal common law governed in the first place was because, as a matter of structural constitutional principles,

“borrowing the law of a particular State would [have been]

inappropriate.” American Electric Power, 564 U.S. at

422. The Clean Air Act obviously did not modify those

principles. And where the Constitution otherwise prohibits the application of state law to an area, “congressional

11

intent must be unmistakably clear” to permit state law to

operate. Wunnicke, 467 U.S. at 91. Indeed, respondents

seemingly admit that, when “federal interests predominate,” the presumption against preemption does not apply. Br. 44. That is exactly the case here.

b. Respondents argue (Br. 27-30) that petitioners’

constitutional theory “conflicts with” Ouellette and American Electric Power. But the opposite is true. In Ouellette, the Court held that the “only” permissible state-law

actions seeking relief for interstate water pollution are

“those specifically preserved by the [Clean Water] Act.”

479 U.S. at 492. It proceeded to conclude that the saving

clause in the Clean Water Act permitted only claims

brought “pursuant to the law of the source State.” Id. at

497. And in American Electric Power, the Court extended the same framework to the Clean Air Act, which

contains a materially identical saving clause. See 564 U.S.

at 429.

Respondents contend that, in Ouellette, the Court determined which actions were preserved by applying “ordinary field and conflict preemption.” Br. 28. But the

Court expressly based its analysis on the premise that

“the control of interstate pollution is primarily a matter of

federal law.” 479 U.S. at 492. The Court reasoned that

the saving clause “specifically preserves” application of

the law of the source State but “does not preclude preemption of the law of an affected State,” thus starting

from the constitutional baseline that federal law applies.

Id. at 493, 497. And it ultimately concluded that “[n]othing in the Act gives each affected State [the] power to regulate discharges” from other States; to do so would allow

a State to “do indirectly what they could not do directly—

regulate the conduct of out-of-state sources.” Id. at 495,

497.

12

To be sure, the Court described the presumption

against preemption in Ouellette, but it explained that the

presumption is limited to the “historic police power of the

States.” 479 U.S. at 491 n.11. Given its statement that

“the control of interstate pollution is primarily a matter of

federal law,” id. at 492, there is no indication that the

Court gave the presumption any meaningful weight. In

any event, there is no basis to apply the presumption

against preemption where, as here, Congress expresses

its intent through a saving clause. Cf. Puerto Rico v.

Franklin California Tax-Free Trust, 579 U.S. 115, 125

(2016).

Finally on this score, respondents point to Puerto Rico

Department of Consumer Affairs v. Isla Petroleum Corp.,

485 U.S. 495 (1988). See Br. 44-45. But there, Congress

repealed a federal law expressly preempting an area of

traditional state authority—thereby reverting to the

baseline of state authority. See 485 U.S. at 500. That is

not the case here.

4. Respondents’ claims fall within the exclusively federal area of interstate pollution because they seek relief

for injuries allegedly caused by greenhouse-gas emissions

worldwide. Respondents contend that their claims are

“fundamentally different” because “they do not seek

abatement of emissions by anyone.” Br. 32. Even if that

were true (despite the numerous references to abatement

in their complaint, see J.A. 2, 79, 117, 136), respondents do

not dispute that they are seeking to recover “billions of

dollars” from petitioners for past and future climatechange harms. See J.A. 1-3, 114, 136-137. It is beyond

disingenuous to suggest that an award of billions of dollars in damages would have no corresponding reduction of

emissions, and this Court has previously rejected similar

efforts to avoid preemption. See Ouellette, 479 U.S. at 498

n.19; Riegel v. Medtronic, Inc., 552 U.S. 312, 324 (2008).

13

The stated intent and obvious effect of this lawsuit—and

the dozens of other coordinated lawsuits—are to impose

climate-change advocates’ preferred policy of limiting

greenhouse-gas emissions by limiting fossil-fuel production.

At various points, respondents seek to categorize their

claims into “sales and production claims” and “deception

claims.” See, e.g., Br. 4. But regardless of whether the

initial conduct being targeted is the act of production or

some related representation, respondents’ claims seek relief for injuries allegedly caused by global climate change

and are thus precluded by the Constitution. A plaintiff

cannot avoid preemption merely by targeting upstream

actors or relabeling its claims. See, e.g., Kurns v. Railroad Friction Products Corp., 565 U.S. 625, 635 (2012).

Respondents offer no valid reason why “sales and production claims” and “deception claims” should be treated differently; as long as the plaintiff is seeking relief for global

climate change, the equal-sovereignty principle applies

equally to both.

Respondents’ last resort is to complain that foreclosing their claims “would invite endless debate over what

other subjects should be declared ‘inherently federal.’ ”

Br. 40. But petitioners’ rule is grounded in history and

precedent and is appropriately limited in scope. Respondents, by contrast, can cite no precedent permitting even

remotely similar state-law claims to go forward. See pp.

14-15, infra.

B. The Constitution Does Not Allow States To Apply

Their Law Extraterritorially To Reach Claims For Injuries From Global Climate Change

It is an “elementary principle” that “the laws of one

State have no operation outside of its territory.” Pennoyer v. Neff, 95 U.S. 714, 722-723 (1877) (citing Joseph

Story, Commentaries on the Conflicts of Laws 28 (5th ed.

14

1857)); see Fuld v. Palestine Liberation Organization,

606 U.S. 1, 14 (2025). The prohibition on extraterritorial

regulation, which is derived from “the Constitution’s horizontal separation of powers,” National Pork Producers

Council v. Ross, 598 U.S. 356, 376 n.1 (2023), independently bars a State from using its law to govern conduct in another State. See Pet. Br. 24, 27-29.

Respondents seek to sidestep the extraterritoriality

principle by invoking a rarely cited exception to it, arguing that there are certain circumstances in which the Constitution permits one State to apply its law to conduct in

another. See Br. 35-38. Petitioners do not dispute that

state law can govern out-of-state conduct where there is a

sufficient connection between the State, the defendant,

and the conduct at issue. See Young v. Masci, 289 U.S.

253, 258-259 (1933). But that exception applies in “ordinary” tort cases, not interstate-pollution disputes. See Illinois v. City of Milwaukee, 731 F.2d 403, 411 n.3 (7th Cir.

1984), cert. denied, 469 U.S. 1196 (1985). And even if it

could apply here, the exception cannot conceivably reach

claims seeking relief for global climate change.

1. To invoke the exception to the extraterritoriality

principle, a plaintiff must show that the out-of-state conduct has direct, traceable, and particularized effects

within the State of the kind that existed in Masci itself.

See 289 U.S. at 258-259; U.S. Br. 21-26. In other words,

the defendant must have a “constructive presence” in the

State, meaning that his conduct must be directed to the

State and produce sufficiently proximate effects there

such that he can be treated as if he were present. See

Strassheim v. Daily, 221 U.S. 280, 285 (1911).

Respondents reject that test, but they struggle to offer one of their own. At times, they seem to suggest that

a State can extraterritorially apply its law to conduct in

another State whenever the conduct has incidental effects

15

within that State, no matter how remote the connection—

an exception that would swallow the extraterritoriality

rule altogether. See Br. 38. But respondents fail to identify any case in which bare harm in a State was sufficient

to give it regulatory authority where the harm was diffused nationwide (and indeed worldwide) and the conduct

was not targeted to the State. Although respondents

claim to have unearthed a long line of cases deciding

“transboundary environmental nuisance claims” under

state law, Br. 39, all they can muster is a smattering of

obviously distinguishable cases concerning damages

caused by the diversion of water from one State to another and corresponding riparian-right disputes. See,

e.g., State v. Lord, 16 N.H. 357 (1844); Stillman v. White

Rock Manufacturing Co., 23 F. Cas. 83, 86 (C.C.D.R.I.

1847). If there were a “long tradition” of applying state

law in this context, Br. 37, one would expect to see better

evidence of it.

At other times, respondents seem to concede that the

effects must have some causal nexus with the conduct.

See Br. 37. But any such nexus here is extremely attenuated; at most, respondents contend that they will be able

to estimate each petitioner’s indirect contribution to

greenhouse-gas emissions and then model how weather

patterns would have changed without those emissions.

See Br. 39 n.14. That falls well short of demonstrating

that the out-of-state conduct has direct, traceable, and

particularized in-state effects. And it is no answer that

some type of causation would be an element of respondents’ state-law claims, see Br. 37-38; the question here is

whether, as a matter of federal constitutional law, extraterritorial regulation is permitted.

Petitioners’ rule, on the other hand, permits extraterritorial regulation in appropriate circumstances. It would

16

not bar the other categories of tort claims that respondents cite, such as those seeking relief for injuries caused

by asbestos, automobile accidents, defamatory articles,

defective medical devices, or Internet fraud. See Br. 2425. In those circumstances, the defendant has engaged in

conduct specifically directed at the forum State, such as

shipping physical products into it. But claims seeking relief for global climate change do not arise from conduct

specifically directed at any particular State. See Pet. Br.

28; U.S. Br. 24. Put simply, there is no way to permit

these claims to proceed without eradicating the

longstanding limitation on extraterritorial regulation and

opening the floodgates to suits across the country targeting the conduct at issue here (and potentially other types

of conduct as well).

2. Respondents suggest (Br. 25-27) that the limitations on state authority inherent in the horizontal separation of powers are fully embodied by the Due Process

Clause, the Full Faith and Credit Clause, and the

dormant Commerce Clause. Those provisions reflect the

Constitution’s basic treatment of the States as territorial

units and evince the Constitution’s concern with extraterritorial regulation by the States. But they do not foreclose

the structural extraterritoriality principle, which is “so

obviously the necessary result of the Constitution that it

has rarely been called into question.” New York Life Insurance Co. v. Head, 234 U.S. 149, 161 (1914).

The Due Process Clause of the Fourteenth Amendment reinforces the limitations on state authority embodied in the original Constitution by imposing restrictions

on personal jurisdiction and choice of law. But the restrictions on personal jurisdiction are designed to protect

the rights of parties; they are not coextensive with the restrictions on a State’s substantive authority. See Phillips

Petroleum Co. v. Shutts, 472 U.S. 797, 814-815 (1985);

17

Strassheim, 221 U.S. at 285. And as this case illustrates,

personal jurisdiction may not provide much protection for

defendants facing such expansive claims; the trial court

relied on petitioners’ in-state conduct as a basis for exercising personal jurisdiction over claims challenging petitioners’ conduct worldwide. See Pet. App. 72a.

The restrictions on choice of law, which are also rooted

in the Full Faith and Credit Clause, likewise do not operate to the exclusion of the extraterritoriality principle.

See Ouellette, 479 U.S. at 499 n.20. And here, respondents

have consistently represented that their claims arise under Colorado law, belying any suggestion that choice-oflaw questions are yet to come. See, e.g., Resp. Colo. S. Ct.

Br. 1, 17, 19, 43; J.A. 130, 133, 136. In any event, the answer would not be to “apply another state’s law.” Br. 26.

Because “greenhouse gases once emitted become well

mixed in the atmosphere,” American Electric Power, 564

U.S. at 422-423, no single State would have any greater

claim to regulation than any other.

The dormant Commerce Clause is related to, yet distinct from, “the territorial limits of state authority under

the Constitution’s horizontal separation of powers.” National Pork Producers, 598 U.S. at 375 n.1. The Constitution “precludes the application of a state statute to commerce that takes place wholly outside of the State’s borders, whether or not the commerce has effects within the

State.” Edgar v. MITE Corp., 457 U.S. 624, 642 (1982)

(plurality opinion); National Pork Producers, 598 U.S. at

375 n.1. Respondents contend that the prohibition on extraterritorial regulation is a “more extreme” version of

the rule rejected in National Pork Producers. Br. 26.

Not so. National Pork Producers concerned a state regulation of in-state conduct that had out-of-state effects.

See 598 U.S. at 371. The Court allowed that regulation to

stand, explaining that, because the regulation had only

18

the “practical effect” of controlling extraterritorial commerce, an “almost per se” rule against its validity was unwarranted. Id. at 374-375. This case concerns the opposite situation: respondents’ attempt to regulate out-ofstate conduct based on in-state effects, which National

Pork Producers expressly distinguished. See id. at 375

n.1. That is the province of the extraterritoriality principle, whose vitality National Pork Producers reaffirmed.

III. THE CONSTITUTION PRECLUDES STATE-LAW

CLAIMS SEEKING RELIEF FOR INJURIES ALLEGEDLY CAUSED BY INTERNATIONAL GREENHOUSE-GAS EMISSIONS

Respondents’ claims are also precluded because they

seek redress for the effects of international emissions.

The federal government agrees, warning that respondents’ lawsuit “invite[s] needless diplomatic friction,” “upend[s]” international negotiations, and “usurps the federal government’s primacy over foreign relations.” U.S.

Br. 3-4, 26-28; see Dkt. 12, at 7-8, United States v. Minnesota, Civ. No. 26-2456 (D. Minn. June 29, 2026) (declaration of Deputy Secretary of State Landau). So do numerous members of Congress and other government officials.

See Scalise Br. 27-30; Cruz Br. 19-22; Senior Foreign Affairs Officials Br. 15-23. Respondents address that independent basis for reversal only in passing, and their arguments are unavailing.

Respondents principally argue (Br. 41) that the presumption against preemption applies in the foreign-affairs context. But as part of the plan of the Convention,

the States relinquished their authority over foreign affairs; that included the power to seek redress not only for

emissions released in other States, but also for those released in other countries. What is more, this lawsuit, and

others like it, target American and foreign corporations

19

alike. See Pet. Br. 42. There is no valid basis for applying

a presumption against preemption in this context.

Respondents suggest (Br. 41) that there is a blanket

rule requiring a “clear conflict” with a treaty or executive

agreement. But the better view is that state law should

give way if it would “impair the effective exercise of the

Nation’s foreign policy,” Zschernig v. Miller, 389 U.S.

429, 440-441 (1968), “even absent any affirmative federal

activity in the subject area of the state law,” American

Insurance Association v. Garamendi, 539 U.S. 396, 418

(2003). The lack of a treaty may reflect nothing more than

the ongoing nature of international negotiations or the

President’s judgment about the national interest. And respondents here do not seriously dispute that their suit

would substantially interfere with the foreign policy of the

United States. See Br. 41-42. When it comes to our Nation’s foreign policy, the President and Congress should

decide the appropriate balance between energy production and greenhouse-gas reduction—not a local jury. See

United States v. Pink, 315 U.S. 203, 233 (1942).

IV. THE CLEAN AIR ACT PREEMPTS STATE-LAW

CLAIMS SEEKING RELIEF FOR INJURIES ALLEGEDLY CAUSED BY EMISSIONS FROM ANOTHER

STATE

A. The Clean Air Act preempts the entire field of interstate air pollution by establishing a comprehensive

statutory scheme for the regulation of air quality across

the United States. See Pet. Br. 44. Respondents contend

(Br. 46) that greenhouse-gas emissions fall outside that

field because of the Environmental Protection Agency’s

recent determination that it would no longer regulate

emissions of greenhouse gases from new motor vehicles.

See 91 Fed. Reg. 7686 (Feb. 18, 2026). But that determination does not apply to EPA’s authority to regulate

greenhouse-gas emissions from stationary sources. See

20

U.S. Br. 34 n.4; 42 U.S.C. 7545(o)(2)(A)(i). Regardless, respondents seemingly do not endorse EPA’s view. See Br.

46; Massachusetts v. EPA, No. 26-1061 (D.C. Cir. filed

Mar. 19, 2026). It is irrelevant to the analysis in any event.

The Clean Air Act “is no less an exercise of the Legislature’s ‘considered judgment’ concerning air pollution because it permits emissions until EPA acts.” American

Electric Power, 564 U.S. at 426. And “[w]here a comprehensive federal scheme intentionally leaves a portion of

the regulated field without controls,” a “pre-emptive inference can be drawn.” Isla Petroleum, 485 U.S. at 503.

That inference would be easy to draw here, given the otherwise comprehensive scope of the Clean Air Act.

Respondents also argue that the Act’s saving clauses

“negat[e]” any inference of field preemption. See Br. 48

(quoting Ouellette, 479 U.S. at 491). Not so. The presence

of an exception to a field does not negate the existence of

the field. See, e.g., Pacific Gas & Electric Co. v. State Energy Resources Conservation & Development Commission, 461 U.S. 190, 212 (1983). Congress intended comprehensively to regulate air quality and provided a specific exception for a source State to regulate its own emissions, including emissions causing harm in another State.

See 42 U.S.C. 7410(a)(2)(D); Cruz Br. 28-29. If anything,

the fact that Congress specified precisely what sort of pollution-abatement laws States may still enact underscores

the Act’s comprehensiveness.

Respondents rely heavily on Virginia Uranium, Inc.

v. Warren, 587 U.S. 761 (2019), see Br. 50-51, but it is not

to the contrary. There, the State regulated in an area of

traditional state authority, see 587 U.S. at 770, and the

state law did not reach conduct within the preempted

field. Here, respondents seek relief for injuries resulting

from interstate greenhouse-gas emissions—which fall

squarely in the field preempted by the Clean Air Act.

21

B. Respondents’ claims also conflict with EPA’s authority to decide “whether and how to regulate” air pollution. American Electric Power, 564 U.S. at 426; see U.S.

Br. 32-34. The assertion of nationwide authority conflicts

with the States’ limited role in implementing federally approved emissions standards, see 42 U.S.C. 7411(c); far exceeds the scope of authority preserved by the Act’s saving

clause, see 42 U.S.C. 7416; and renders obsolete the Act’s

“Good Neighbor” provision, see 42 U.S.C. 7410(a)(2)

(D)(i).

Respondents contend that their suit does not interfere

with EPA’s role as the “first decider” because their claims

regulate “deception” and “sales and production.” Br. 4751. That is a distinction without a difference. See American Trucking Associations v. City of Los Angeles, 569

U.S. 641, 652 (2013). Because respondents seek relief for

injuries allegedly caused by global climate change, their

claims conflict with EPA’s determinations of whether and

how to regulate emissions. See U.S. Br. 29-30.

To be sure, not all state regulations of conduct affecting the level of nationwide greenhouse-gas emissions conflict with the Clean Air Act. For example, gasoline taxes

and energy-efficiency standards validly regulate in-state

conduct. And the Act’s saving clause authorizes States to

regulate in-state emissions. See 42 U.S.C. 7416; Bell v.

Cheswick Generating Station, 734 F.3d 188, 196 (3d Cir.

2013), cert. denied, 572 U.S. 1149 (2014). But respondents’

claims do far more, by inviting state juries to determine

what constitutes a reasonable level of greenhouse-gas

emissions worldwide. See Public Service Co. v. Van Wyk,

27 P.3d 377, 391 (Colo. 2001); American Electric Power,

564 U.S. at 428-429. In so doing, respondents’ claims intolerably interfere with EPA’s role as the “primary regulator of greenhouse-gas emissions.” American Electric

Power, 564 U.S. at 427-428.

22

*

*

*

*

*

The stakes in this case—not only for the parties but

for the entire legal system—could not be higher. If this

Court allows the Colorado Supreme Court’s decision to

stand, it would be blessing the weaponization of state law

and sanctioning lawfare in the state courts, by any State

or municipality, against one of the Nation’s most important industries—an industry that, by providing reliable, affordable energy, is essential to promoting and sustaining our modern way of life.

Climate change is a real and pressing issue. But such

a global issue should be solved by political actors on the

national and international level through a comprehensive

regulatory regime, not decided by hundreds of juries on

the local level in cases brought against an arbitrary selection of defendants. Where a plaintiff seeks relief for injuries allegedly caused by global climate change, the plaintiff cannot resort to state law. The judgment of the Colorado Supreme Court should be reversed.

Respectfully submitted.

HUGH QUAN GOTTSCHALK

ERIC L. ROBERTSON

WHEELER TRIGG

O’DONNELL LLP

370 Seventeenth Street,

Suite 4500

Denver, CO 80202

KANNON K. SHANMUGAM

JAKE L. KRAMER

ELEANOR K. RITTER

KEITH E. ZIMMERMAN

DAVIS POLK & WARDWELL LLP

1050 17th Street, N.W.

Washington, DC 20036

(202) 962-7000

kshanmugam@davispolk.com

Counsel for Petitioners

Suncor Energy (U.S.A.) Inc.

and Suncor Energy Sales Inc. Counsel for Petitioner

Exxon Mobil Corporation

AUGUST 2026