Amicus Curiae 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.,

Respondents.

___________

On Writ of Certiorari

to the Supreme Court of Colorado

___________

BRIEF OF AMICI CURIAE SENIOR FOREIGN

AFFAIRS OFFICIALS MICHAEL R. POMPEO,

JAMES ADDISON BAKER III, NIKKI HALEY,

AND HERBERT R. MCMASTER

IN SUPPORT OF PETITIONERS

___________

WILLIAM P. BARR

CODY L. REAVES*

L. PATRICK ELLIS II

TORRIDON LAW PLLC

801 17th Street, NW

Suite 1100

Washington, D.C. 20006

(202) 249-6900

creaves@torridonlaw.com

Counsel for Amici Curiae

May 21, 2026

* Counsel of Record

TABLE OF CONTENTS

Page

TABLE OF AUTHORITIES ........................................ ii

INTEREST OF AMICI CURIAE ................................. 1

INTRODUCTION

AND

SUMMARY

OF

ARGUMENT........................................................... 2

ARGUMENT ................................................................ 5

I. Power Over Foreign Affairs Is Vested

Exclusively In The Federal Government............... 5

II. Foreign Affairs Preemption Applies Where A

State Law Interferes With The Federal

Government’s Conduct Of Foreign Relations. ....... 7

III.Presidential And Congressional Actions Across

Decades Demonstrate A Concerted Policy

Decision To Address International Greenhouse

Gas Emissions With Foreign Governments. ....... 15

IV. State Laws Regulating U.S. Companies’

Alleged Contributions To Global Emissions

Interfere With The Federal Government’s

Conduct Of Foreign Relations.............................. 23

CONCLUSION .......................................................... 27

(i)

ii

TABLE OF AUTHORITIES

Page(s)

Cases

Am. Ins. Ass’n v. Garamendi,

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

Banco Nacional de Cuba v. Sabbatino,

376 U.S. 398 (1964) .............................................. 12

Boyle v. United Tech. Corp.,

487 U.S. 500 (1988) ................................................ 7

Chicago & Southern Air Lines, Inc. v.

Waterman S. S. Corp.,

333 U.S. 103 (1948) ................................................ 7

City of New York v. Chevron,

993 F.3d 81 (2d Cir. 2021) .................................... 24

Crosby v. Nat’l Foreign Trade Council,

530 U.S. 363 (2000) .......................................passim

Dames & Moore v. Regan,

453 U.S. 654 (1981) .............................................. 26

Fuld v. Palestine Liberation Org.,

606 U.S. 1 (2025) .................................................... 5

Haig v. Agee,

453 U.S. 280 (1981) .............................................. 11

Hencely v. Fluor Corp.,

608 U.S. ----, 146 S. Ct. 1086 (2026) ...................... 7

iii

TABLE OF AUTHORITIES—continued

Hines v. Davidowitz,

312 U.S. 52 (1941) .......................................... 2, 5, 6

Learning Res., Inc. v. Trump,

146 S. Ct. 628 (2026) ............................................ 11

M’Culloch v. Maryland,

4 Wheat. 316 (1819)................................................ 8

Medellin v. Texas,

552 U.S. 491 (2008) .............................................. 15

Osborn v. Bank of United States,

9 Wheat. 738 (1824)................................................ 8

United States v. Belmont,

301 U.S. 324 (1937) ........................................ 5, 7, 8

United States v. Curtiss-Wright Export

Corp.,

299 U.S. 304 (1936) ...................................... 2, 5, 17

United States v. Pink,

315 U.S. 203 (1942) .......................................passim

United States v. Standard Oil Co. of

Cal.,

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

Youngstown Sheet & Tube Co. v.

Sawyer,

343 U.S. 579 (1952) .............................................. 11

Zschernig v. Miller,

389 U.S. 429 (1968) ...................................... 7, 9, 10

iv

TABLE OF AUTHORITIES—continued

Statutes

42 U.S.C. § 7543(a) .................................................... 22

Other Authorities

162 Cong. Rec. S1886 (daily ed. Apr. 12,

2016)...................................................................... 18

A Greener Bush, The Economist (Feb.

13, 2003), tinyurl.com/BushRio ........................... 17

Barack Obama, Remarks by the

President at U.N. Climate Change

Summit (Sept. 23, 2014),

https://tinyurl.com/ObamaOnClimate ................... 4

Barack Obama, Remarks by the

President on Climate Change (June

25, 2013), tinyurl.com/ObamaGeorgetown ....................... 19, 20

Benjamin M. Barczewski, Kathryn G.

Kynett & Emily N. Peterson, CONG.

RSCH. SERV., R48168, California and

the Clean Air Act (CAA) Waiver:

Frequently Asked Questions (2025),

https://tinyurl.com/CAAWaiverCRS. ................... 23

George W. Bush, President Bush

Discusses Global Climate Change

(June 11, 2001),

https://tinyurl.com/BushOnClimate ................ 4, 19

v

TABLE OF AUTHORITIES—continued

Joseph R. Biden & Ursula von der

Leyen, Joint Statement by President

Biden and President Ursula von der

Leyen of the European Commission

on European Energy Security (June

27, 2022),

https://tinyurl.com/BidenOnEnergy .................... 20

L. Henkin, Foreign Affairs and the

United States Constitution, 219, 496

n.163 (2d ed. 1996). .............................................. 13

Montreal Protocol on Substances that

Deplete the Ozone Layer, Sept. 16,

1987, S. Treaty Doc. No. 100-10, 1522

U.N.T.S.3 .............................................................. 17

Report of the United Nations Conference

on Environment and Development,

Vol.

I

(June

13,

1992),

tinyurl.com/RioDec ............................................... 18

Richard M. Nixon, Statement About the

United Nations Conference on the

Human Environment in Stockholm,

Sweden (June 20, 1972),

https://tinyurl.com/NixonOnStockhol

m ........................................................................... 16

Ronald Reagan, Statement on Signing

the Montreal Protocol on OzoneDepleting Substances (Apr. 5, 1988),

tinyurl.com/RgnMtrlPrtcl .................................... 17

S. Res. 98, 105th Cong. (1997)................................... 22

vi

TABLE OF AUTHORITIES—continued

U.S. Const. art. I, § 10, cl. 1......................................... 5

U.S. Const., art. II, § 2, cl. 2 ...................................... 10

U.S. Dep’t of Energy, ICYMI: Energy

Secretary Chris Wright Delivers

Remarks in Riyadh Following U.S.Saudi Energy Cooperation MOU

Announcement (Apr. 15, 2025),

https://tinyurl.com/TrumpSaudiMOU ................. 21

U.S. Dep’t of Energy, Office of Energy

Dominance Financing (last visited

May 13, 2026) ....................................................... 23

U.S. Dep’t of Energy, Secretary Wright

Signs Agreements To Grow American

LNG Exports, Advances ‘Trump

Peace Pipelines Framework’ (Apr. 28,

2026),

https://tinyurl.com/TrumpPeacePipeli

nes ......................................................................... 21

U.S. Dep’t of the Interior, Interior Dep’t

Advances Energy Dominance

Through the One Big Beautiful Bill

Act (July 22, 2025),

https://tinyurl.com/DOIEnergyDomin

ance ....................................................................... 23

United Nations, Report of the United

Nations Conference on the Human

Environment, 5 (1973),

https://tinyurl.com/StockholmDecl ...................... 16

vii

TABLE OF AUTHORITIES—continued

United States and China Reach

Agreement on Phase Down of HFCs

(Sept. 6, 2013),

https://tinyurl.com/ObamaOnCFCs ..................... 20

William J. Clinton, Remarks at the

National Geographic Society (Oct. 22,

1997),

https://tinyurl.com/ClintonOnClimate .................. 4

Withdrawing the United States from

International Organizations,

Conventions, and Treaties that Are

Contrary to the Interests of the United

States (Jan. 7, 2026),

https://tinyurl.com/TrumpUNFCCC .................... 18

INTEREST OF AMICI CURIAE1

Amici are former senior foreign policy officials of the

United States. In these roles, they saw firsthand the

nature of international negotiation and the paramount

importance of the United States speaking with one

voice when engaging with other countries.

Michael R. Pompeo served as the 70th United States

Secretary of State from 2018 to 2021. Before his service as Secretary of State, Mr. Pompeo served as the

6th Director of the Central Intelligence Agency from

2017 to 2018 and represented the Fourth District of

Kansas in the United States House of Representatives

from 2011 to 2017.

James Addison Baker III served as the 61st United

States Secretary of State from 1989 to 1992 and the

67th United States Secretary of the Treasury from

1985 to 1988. Both before and after his service in those

roles, Mr. Baker served as White House Chief of Staff,

first for President Ronald Reagan from 1981 to 1985,

and then President George H.W. Bush from 1992 to

1993.

Nikki Haley served as the 29th United States Ambassador to the United Nations from 2017 to 2018. Before her service in that role, Ms. Haley served as the

Governor of South Carolina from 2011 to 2017.

Herbert R. McMaster served as the 25th United

States National Security Advisor from 2017 to 2018.

He is a retired Lieutenant General in the U.S. Army.

1 Per Rule 37.6, amicus curiae states that no counsel for any

party authored this brief in any part, and that no person or entity

other than amicus or its counsel made a monetary contribution to

fund its preparation or submission.

2

INTRODUCTION AND

SUMMARY OF ARGUMENT

The decision below defies our Constitution’s text,

structure, and history, along with this Court’s precedents.

The Constitution vests power over foreign affairs exclusively in the federal government. In defending our

national charter and urging its ratification, the Founders made clear that, on issues related to foreign powers, our nation must be united and speak with one

voice. And as this Court has long held, our Constitution’s text and structure establish the “plenary and exclusive power … of the federal government in the field

of international relations.” United States v. CurtissWright Export Corp., 299 U.S. 304, 320 (1936). The

President and Congress thus together have the power

to tackle the “important, complicated, delicate, and

manifold problems” that arise in the “vast external

realm.” Id. at 319.

Like our Founders, this Court has recognized that

our Constitution establishes a system of government

“such that the interest of the cities, counties and

states, no less than the interest of the people of the

whole nation, imperatively requires that federal power

in the field affecting foreign relations be left entirely

free from local interference.” Hines v. Davidowitz, 312

U.S. 52, 63 (1941) (emphasis added). That means

“state laws and policies” must “yield before the exercise of the external powers of the United States.”

United States v. Pink, 315 U.S. 203, 232 (1942). Accordingly, when a state law is likely to “produce something more than incidental effect in conflict with express foreign policy of the National Government,” the

Constitution “require[s] preemption of the state law.”

Am. Ins. Ass’n v. Garamendi, 539 U.S. 396, 420 (2003).

3

Boulder’s lawsuit plainly does just that. It necessarily intrudes on the United States’ foreign affairs

power and undermines the national government’s ability to address the issues of global climate change on

the international stage—the only arena in which these

matters can be realistically and equitably handled.

The suit’s premise is that Boulder has been damaged

by global climate change. See Pet. App. 1a-2a (seeking

damages “for the role that [petitioners’] production,

promotion, refining, marketing, and sale of fossil fuels

has allegedly played in exacerbating climate change.”

(emphasis added)). Thus, the physical mechanism

that is allegedly injuring Colorado—the prevalence of

greenhouse gases in Earth’s atmosphere—is not a local one, but a global one caused by everyone’s emissions everywhere on the planet. The emissions targeted by Boulder’s suit, moreover, are the worldwide

emissions of particular companies in relation to all

emissions that have historically occurred globally. See

Pet. App. 2a (noting that Boulder alleges injury from

“the impacts of climate change”).

Boulder’s action thus seeks relief from particular

American companies based on the extent to which each

company’s actions worldwide have contributed to

global climate change. Under this regime, Colorado

state court juries will determine what share of global

climate change each American company should be

held responsible for—as opposed to, say, China’s

roughly 1,100 coal-fired power plants, Russia’s highmethane emissions, or Brazil’s carbon-intensive deforestation and agricultural practices. Allowing local

state juries to make decisions regarding—and impose

liability for—American companies’ relative contributions to global climate change plainly impairs the federal government’s ability to address issues related to

global greenhouse gas emissions and climate change

4

through international collaboration and coordination,

and interferes with the United States’ longstanding

policy that “[c]limate change, with its potential to impact every corner of the world, is an issue that must be

addressed by the world.” George W. Bush, President

Bush Discusses Global Climate Change (June 11,

2001), https://tinyurl.com/BushOnClimate.2

Within this diplomatic process, it is the national government’s role to frame and advance a national position on relative responsibility for climate change and a

fair means of addressing it, and to negotiate bilateral

and multilateral agreements to effectuate those national objectives. Permitting individual states to

frame their own regimes for regulating global emissions and local juries to allocate the proportionate responsibility of American companies undercuts the

President’s ability to engage in “effective diplomacy”

by “compromis[ing] the very capacity of the President

to speak for the Nation with one voice in dealing with

other governments.” Crosby v. Nat’l Foreign Trade

Council, 530 U.S. 363, 381 (2000).

Amici urge the Court to reverse the decision below

and to reaffirm that, where state law is likely to produce “something more than incidental effect in conflict

with express foreign policy of the National Government,” the Constitution “require[s] preemption of the

state law.” Garamendi, 539 U.S. at 420.

2 See William J. Clinton, Remarks at the National Geographic So-

ciety (Oct. 22, 1997), https://tinyurl.com/ClintonOnClimate (“The

countries of the world [must] work together to cut the emission of

greenhouse gases.”); Barack Obama, Remarks by the President at

U.N. Climate Change Summit (Sept. 23, 2014), https://tinyurl.com/ObamaOnClimate (“We can only succeed in combating

climate change if we are joined in this effort by every nation.”).

5

ARGUMENT

I. POWER OVER FOREIGN AFFAIRS IS

VESTED EXCLUSIVELY IN THE FEDERAL

GOVERNMENT.

As this Court has long recognized, the Constitution’s

text, structure, and history entrust the federal government “with full and exclusive responsibility for the

conduct of affairs with foreign sovereignties.” Hines v.

Davidowitz, 312 U.S. 52, 63 (1941); see U.S. Const. art.

I, § 10, cl. 1. “Government power over internal affairs”

is, of course, “distributed between the national government and the several states.” United States v. Belmont, 301 U.S. 324, 330 (1937). But in the realm of

foreign affairs, both the “origin and essential character” of “federal power” is “different.” United States v.

Curtiss-Wright Export Corp., 299 U.S. 304, 319 (1936).

When the colonies, “acting as a unit,” separated from

Great Britain, “the powers of external sovereignty

passed from the Crown … to the Union.” Id. at 31617. “[S]ince the states severally never possessed international powers, such powers could not have been

carved from the mass of state powers.” Id. at 316.

“Government[] power over external affairs” thus is

“not distributed, but is vested exclusively in the national government.” Belmont, 301 U.S. at 330; see

Fuld v. Palestine Liberation Org., 606 U.S. 1, 15 (2025)

(“The Constitution confers upon the Federal Government—and it alone—both nationwide and extraterritorial authority.”).

The Framers’ persistent defense of the need for exclusive federal control over foreign affairs only underscores this understanding. James Madison made clear

that “[i]f we are to be one nation in any respect, it

clearly ought to be in respect to other nations,” The

Federalist No. 42 (J. Madison), and emphasized “the

6

advantage of uniformity in all points which related to

foreign powers,” The Federalist No. 44 (J. Madison).

The United States “will undoubtedly be answerable to

foreign powers for the conduct of its members,” Alexander Hamilton recognized, and “the WHOLE ought

not be left at the disposal of PART.” The Federalist

No. 80 (A. Hamilton); see Letter from Thomas Jefferson to James Madison (Feb. 8, 1786), in 1 The Republic

of Letters: The Correspondence between Thomas Jefferson and James Madison 1776-1826, at 409, 410

(James Morton Smith ed., 1995) (emphasizing that it

is “indispensably necessary that with respect to every

thing external we be one nation only, firmly hooped together”).

Indeed, the system of government enshrined in our

Constitution “is such that the interest of the cities,

counties and states, no less than the interest of the

people of the whole nation, imperatively requires that

federal power in the field affecting foreign relations be

left entirely free from local interference.” Hines, 213

U.S. at 63 (emphasis added). This Court—like our

Founders—has recognized that, “[i]f state laws and

policies did not yield before the exercise of the external

powers of the United States, then our foreign policy

might be thwarted” and “serious consequences might

ensue.” Pink, 315 U.S. at 232; see The Federalist No.

4 (J. Jay) (“If [foreign nations] find us either destitute

of an effectual government (each State doing right or

wrong, as its rulers may seem convenient) … what a

poor, pitiful figure will America make in their eyes!”).3

3 While the President and Congress share this exclusive federal

power, in this “vast external realm, with its important, complicated, delicate, and manifold problems, the President alone has

the power to speak or listen as a representative of the nation.”

Curtiss-Wright, 299 U.S. at 319. The President’s authority to conduct foreign affairs involves “the very delicate, plenary and exclusive power … as the sole organ of the federal government in the

7

In the end, text, structure, and history all demand

that the “external powers of the United States are to

be exercised without regard to state laws or policies.”

Belmont, 301 U.S. at 331.

II. FOREIGN AFFAIRS PREEMPTION APPLIES WHERE A STATE LAW INTERFERES

WITH THE FEDERAL GOVERNMENT’S

CONDUCT OF FOREIGN RELATIONS.

From the federal government’s exclusive power over

foreign relations flows the doctrine of foreign affairs

preemption. The core of foreign affairs preemption is

“beyond dispute”: “[A]t some point an exercise of state

power that touches on foreign relations must yield to

the National Government’s policy.” Garamendi, 539

U.S. at 413. Although the precise contours of this doctrine have long been debated, this Court has made

clear that “state laws ‘must give way if they impair the

effective exercise of the Nation’s foreign policy.’” Id. at

419 (quoting Zschernig v. Miller, 389 U.S. 429, 440

(1968)); Pink, 315 U.S. at 230-31.

When a state law intrudes in an exclusively federal

domain, the “conflict with federal policy need not be as

sharp as that which must exist for ordinary pre-emption when Congress legislates ‘in a field which the

States have traditionally occupied.’” Boyle v. United

Tech. Corp., 487 U.S. 500, 507 (1988) (quotation omitted); see Hencely v. Fluor Corp., 608 U.S. ----, 146 S.

Ct. 1086, 1103 (2026) (Alito, J., dissenting) (explaining

that “[p]reemption based on constitutional structure”

field of international relations—a power which does not require

as a basis for its exercise an act of Congress.” Id. at 320; see Chicago & Southern Air Lines, Inc. v. Waterman S. S. Corp., 333 U.S.

103, 109 (1948) (“The President … possesses in his own right certain powers conferred by the Constitution on him as Commanderin-Chief and as the Nation’s organ in foreign affairs.”).

8

is “especially important” when state law intrudes on

the federal government’s “exclusive authority to conduct relations with other nations”). Accordingly,

where state law is likely to “produce something more

than incidental effect in conflict with express foreign

policy of the National Government,” the Constitution

“require[s] preemption of the state law.” Garamendi,

539 U.S. at 420.

Time and again, the Court has applied this doctrine

to set aside state laws that interfere with the federal

government’s conduct of foreign relations by standing

in the way of the federal government’s diplomatic objectives expressed through compacts, executive agreements, and foreign affairs policies.4

1. In United States v. Belmont, 301 U.S. 324 (1937),

the Court held that diplomatic compacts entered into

by the President, even without Senate ratification,

trigger foreign affairs preemption. The Court held

that, because government power “over external affairs … is vested exclusively in the national government,” “the external powers of the United States are

to be exercised without regard to state law or policies.”

Id. at 330-31. The supremacy of “all international

compacts and agreements” flows “from the very fact

that complete power over international affairs is in the

national government and is not and cannot be subject

4 The Court has likewise held that federal law preempts state

laws that intrude on the powers that the Constitution confers exclusively on the federal government. See M’Culloch v. Maryland,

4 Wheat. 316 (1819); Osborn v. Bank of United States, 9 Wheat.

738 (1824); cf. United States v. Standard Oil Co. of Cal., 332 U.S.

301, 307 (1947) (recognizing that M’Culloch and Osborn identified

fields that are “exclusively federal, because made so by constitutional or valid congressional command,” or because they “so vitally affect[ ] interests, powers and relations of the Federal Government as to require uniform national disposition”).

9

to any curtailment or interference on the part of the

several states.” Id. at 331. The Court ultimately rejected New York’s public policy against recognizing

confiscation of private property by foreign governments in categorical fashion, concluding that it is “inconceivable” that any state law “can be interposed as

an obstacle to the effective operation of a federal constitutional power.” Id. at 332.

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

Court reaffirmed and extended Belmont, holding that

such executive agreements have “a similar dignity” to

treaties as the supreme law of the land under the Supremacy Clause. The Court reasoned that “state law

must yield when it is inconsistent with or impairs the

policy or provisions of a treaty or of an international

compact or agreement.” Id. at 230-31. And the Court

once again expressed a sweeping understanding of federal exclusivity in the area of foreign affairs: “No State

can rewrite our foreign policy to conform to its own domestic policies. Power over external affairs is not

shared by the States; it is vested in the national government exclusively.” Id. at 233.

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

Court further expanded foreign affairs preemption,

adopting a form of structural field preemption rooted

not in any executive policy, but in the Constitution’s

allocation of foreign affairs power to the federal government. There, the Court analyzed an Oregon probate statute that allowed nonresident aliens to inherit

from Oregon estates only if their home country

granted reciprocal inheritance rights. The Court held

that the state law was preempted, reasoning that “the

history and operation of this Oregon statute make

clear that [it] is an intrusion by the State into the field

of foreign affairs which the Constitution entrusts to

the President and the Congress.” Id. at 432. The

10

Court noted that the state law “illustrate[d] the dangers which are involved if each State, speaking

through its probate courts, is permitted to establish its

own foreign policy.” Id. at 441. Notably, the Court

recognized that even state regulations in areas of “traditional competence” (like probate law) “must give way

if they impair the effective exercise of the nation’s foreign policy.” Id. at 440, 459.

2. More recently, in Crosby v. National Foreign

Trade Council, 530 U.S. 363 (2000), the Court held invalid under the Supremacy Clause a Massachusetts

law that imposed restrictions on the ability of Massachusetts and its agencies to purchase goods from companies that did business with Burma because the state

law threatened to frustrate Congress’s objectives in a

federal statute imposing mandatory and conditional

sanctions on Burma. Id. at 368.

Although the federal statute lacked an express

preemption provision, the Court reasoned that the

state law “undermine[d] the intended purpose and

‘natural effect’” of “at least three provisions of the federal Act,” including “the President’s intended authority to speak for the United States among the world’s

nations in developing a ‘comprehensive multilateral

strategy” related to Burma. Id. at 373-74, 380. Notably, the Court recognized that “Congress’s explicit delegation to the President … to take the initiative for the

United States among the international community invested him with the maximum authority of the National Government, in harmony with the President’s

own constitutional powers.” Id. at 381 (emphasis

added) (citing U.S. Const., art. II, § 2, cl. 2; § 3).

Even more, the Court reiterated that the state law

“undermine[d] the President’s capacity” for “effective

diplomacy” by “compromis[ing] the very capacity of the

President to speak for the Nation with one voice in

11

dealing with other governments.” Id. The Court noted

that it “need not get into any general consideration of

limits of state action affecting foreign affairs to realize

that the President’s maximum power to persuade rests

on his capacity to bargain for the benefits of access to

the entire national economy without exception for enclaves fenced off willy-nilly by inconsistent political

tactics.” Id. When state laws interfere with the President’s “capacity to present a coherent position on behalf of the national economy,” the Court explained, the

President “is weakened … not only in dealing with”

one foreign nation, “but in working together with other

nations in hopes of reaching common policy and a ‘comprehensive’ strategy.” Id. at 382.

To be sure, Crosby involved statutory preemption of

state law. But as the Court explained just a few years

later, the Court “in Crosby [was] careful to note that

the President possesses considerable independent constitutional authority to act on behalf of the United

States on international issues,” and that “conflict with

the exercise of that authority is a comparably good reason to find preemption of state law.” Garamendi, 539

U.S. at 424 n.14. So too, “[g]iven the President’s independent authority ‘in the areas of foreign policy and

national security, … congressional silence is not to be

equated with congressional disapproval.’” Id. at 429

(quoting Haig v. Agee, 453 U.S. 280, 291 (1981)); see

Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579,

610-11 (1952) (Frankfurter, J., concurring) (recognizing that the President possesses the “vast share of responsibility for the conduct of our foreign relations”);

cf. Learning Res., Inc. v. Trump, 146 S. Ct. 628, 715

(2026) (Kavanaugh, J., dissenting) (same).

3. Finally, in American Insurance Association v. Garamendi, 539 U.S. 396 (2003), the Court held that executive agreements and presidential foreign policy—

12

even without explicit congressional authorization—

preempted conflicting state law. There, California’s

Holocaust Victim Insurance Relief Act of 1999

(HVIRA) required any insurer doing business in California to disclose information about insurance policies

sold in Europe between 1920 and 1945 under penalty

of loss of the insurer’s state business license. Id. at

401. The federal government argued that this state

law scheme “interfere[d] with foreign policy of the Executive Branch, as expressed principally in the executive agreements with Germany, Austria, and France,”

which established a voluntary framework for resolving

Holocaust-era insurance claims through diplomatic

consensus rather than state coercion. Id. at 413.

The Court began by recognizing that, “given the ‘concern for uniformity in this country’s dealings with foreign nations’ that animated the Constitution’s allocation of the foreign relations power to the National Government in the first place,” “at some point an exercise

of state power that touches on foreign relations must

yield to the National Government’s policy.” Id. at 413

(quoting Banco Nacional de Cuba v. Sabbatino, 376

U.S. 398, 427 n.25 (1964)). Nor could there be “any

question” that the President has “authority to decide

what that policy should be.” Id. at 414; see Youngstown, 343 U.S. at 635-36 n.2 (Jackson, J., concurring

in judgment and opinion of Court) (the President can

“act in external affairs without congressional authority”).

This authority has—“since the early years of our Republic”—included the power “to make executive agreements with other countries, requiring no ratification

by the Senate or approval by Congress.” Garamendi,

539 U.S. at 415 (collecting cases). Indeed, “Presidents

from Washington to Clinton,” and Bush to Obama, and

Biden to Trump “have made many thousands of

13

agreements … on matters running the gamut of U.S.

foreign relations.” L. Henkin, Foreign Affairs and the

United States Constitution, 219, 496 n.163 (2d ed.

1996).5 Against this backdrop, the Court concluded

that “valid executive agreements are fit to preempt

state law, just as treaties are.” Garamendi, 539 U.S.

at 416.

The executive agreements in Garamendi, however,

included no preemption provisions. So the federal government’s claim of preemption rested on “asserted interference with the foreign policy those agreements

embody.” Id. at 417. After canvassing its foreign-affairs-preemption cases, the Court reasoned that state

laws “must give way if they impair the effective exercise of the Nation’s foreign policy,” and that “the likelihood that state legislation will produce something

more than incidental effect in conflict with express foreign policy of the National Government would require

preemption of the state law.” Id. at 419-20 (citation

omitted). The Court further explained that courts

should “consider the strength of the state interest,

judged by standards of traditional practice, when deciding how serious a conflict must be shown before declaring the state law preempted.” Id. at 420 (citing

5 The Court explained that, although the executive agreements at

issue in Garamendi differed from past agreements in that they

dealt with claims “against corporations” rather than “foreign governments,” this “distinction does not matter.” Id. at 416. While

a “sharp line” works for many purposes in the domestic law, insisting on the same line in defining the legitimate scope of the

Executive’s international negotiations “would hamstring the

President in settling international controversies.” Id.; see Pink,

315 U.S. at 234-42 (Frankfurter, J., concurring) (noting the unsoundness of transplanting “judicial subtleties” of domestic law

into “the solution of analogous problems between friendly nations”).

14

Southern Pacific Co. v. Arizona ex rel. Sullivan, 325

U.S. 761, 768-69 (1945).

In applying this test, the Court recognized that vindicating victims injured by acts in wartime is “within

the traditional subject matter of foreign policy” that

the federal government has addressed. Id. at 420-21.

And the state statute—like the Massachusetts law in

Crosby—employed “a different, state system of economic pressure” that “undercuts the President’s diplomatic discretion and the choice he has made exercising

it.” Id. 423-24. While the President’s exercise of authority required “flexibility in wielding ‘the coercive

power of the national economy’ as a tool of diplomacy,”

the state law—if upheld—would leave “the President

[with] less to offer and less economic and diplomatic

leverage as a consequence.” Id. (quoting Crosby, 530

U.S. at 377). The state law thus “compromise[d] the

very capacity of the President to speak for the Nation

with one voice in dealing with other governments” in

conducting foreign affairs. Id. at 424 (citation omitted).

The Court also concluded that the state statute

“threaten[ed] to frustrate the operation of the particular mechanism the President has chosen.” Id. In particular, the Court pointed to letters from California

state officials showing “well enough how the portent of

further litigation and sanctions has in fact placed the

Government at a disadvantage in obtaining practical

results from persuading foreign government and foreign companies to participate voluntarily” in the

framework established through executive agreements.

Id. (quotation omitted). At bottom, the state statute

stood as “an obstacle to the success of the National

Government’s chosen ‘calibration of force’ in dealing

with” foreign nations using its chosen approach. Id. at

425 (quoting Crosby, 530 U.S. at 380).

15

This “express federal policy” and the “clear conflict”

raised by the California statute were “alone enough to

require state law to yield.” Id. But the Court also

noted the “weakness of the State’s interest” in “regulating disclosure of European Holocaust-era insurance

policies.” Id. In the end, the Court explained, California sought “to use an iron fist where the President has

consistently chosen kid gloves.” Id. at 427. The Court

made clear that preemption does not turn on the “wisdom of the National Government’s policy.” Id. Rather,

the “question relevant to preemption” is conflict, and a

state law must fall when it “stands in the way of [the

President’s] diplomatic objectives.”

Id. (quoting

Crosby, 530 U.S. at 386). In the end, the Court held

that the California statute “interferes with the National Government’s conduct of foreign relations” and

thus “is preempted.” Id. at 401.6

III. PRESIDENTIAL AND CONGRESSIONAL

ACTIONS ACROSS DECADES DEMONSTRATE A CONCERTED POLICY DECISION TO ADDRESS INTERNATIONAL

GREENHOUSE GAS EMISSIONS WITH

FOREIGN GOVERNMENTS.

For the past five decades, addressing global greenhouse gas emissions has been a foreign affairs issue

dealt with by the President and Congress—not states.

6 The Court’s decision in Medellin v. Texas, 552 U.S. 491 (2008),

does not undermine Garamendi or its foreign-affairs-preemption

decisions in Pink and Belmont. In Medellin, the Court simply reiterated that the “President’s authority to act” must “stem either

from an act of Congress or from the Constitution itself,” 552 U.S.

at 524 (quotation omitted), and clarified that the President cannot unilaterally transform non-self-executing international obligations into domestic law that overrides state criminal proceedings.

16

Often, this has resulted in the United States spearheading international collaboration on the issue. But

just as critically, it has also required the federal government to oppose international efforts adverse to

United States interests.

1. Presidential Action. Since the early 1970s, the

President and Executive Branch officials have led the

charge in working with foreign nations to address issues related to the effects of global greenhouse gas

emissions.

In 1972, President Nixon sent a delegation to the

United Nations Conference on the Human Environment held in Stockholm, Sweden, the U.N.’s first attempt to encourage international cooperation to preserve natural resources and the environment. That

conference culminated in 26 principles developed to

guide coordinated international responses to potential

environmental threats. Critically, those principles announced a resolve to develop “international law regarding liability and compensation” for harm caused

“by activities within the jurisdiction or control of such

[Nations] to areas beyond their jurisdiction.” United

Nations, Report of the United Nations Conference on

the Human Environment, 5 (1973), https://tinyurl.com/StockholmDecl (Principle 22). Nixon hailed

the Stockholm Conference as a multilateral success,

noted that the U.S. “achieved practically all of its objectives at Stockholm,” and declared that the United

States, working alongside fellow members of the

United Nations, would take “a leading role in international environmental cooperation.” Richard M. Nixon,

Statement About the United Nations Conference on the

Human Environment in Stockholm, Sweden (June 20,

1972), https://tinyurl.com/NixonOnStockholm.

In the late 1980s, President Reagan directed the

United States’ instrumental role in the negotiation

17

and adoption of the Montreal Protocol on Substances

that Deplete the Ozone Layer, an international treaty

that bound signatory nations to freeze— and, later, to

reduce—certain greenhouse gas emissions believed to

be eliminating Earth’s ozone layer. Montreal Protocol

on Substances that Deplete the Ozone Layer, Sept. 16,

1987, S. Treaty Doc. No. 100-10, 1522 U.N.T.S. 3. The

Montreal Protocol, unanimously ratified by the Senate

in 1988, has—perhaps more than any other diplomatic

agreement—guided the United States’ and United Nations’ responses to global greenhouse gas emissions.

Its legacy is astonishing—it was the first treaty in

United Nations’ history to be ratified by every member

state. As President Reagan put it, the Montreal Protocol is a “model of cooperation” and the product “of the

recognition and international consensus” that addressing global emissions “is a global problem.”

Ronald Reagan, Statement on Signing the Montreal

Protocol on Ozone-Depleting Substances (Apr. 5, 1988),

tinyurl.com/RgnMtrlPrtcl (emphasis added). Unanimous consensus in international affairs is rare, but on

this the world agrees: Solving this global problem will

require a globally concerted solution.

In the Montreal Protocol’s wake, President George

H.W. Bush and Secretary of State James Baker orchestrated the United States’ involvement in negotiations at the 1992 Earth Summit in Rio De Janeiro. Before the Summit, President H.W. Bush reportedly forecast that the “American way of life” would not be “up

for negotiation.” A Greener Bush, THE ECONOMIST

(Feb. 13, 2003), tinyurl.com/BushRio. This remark

demonstrates the delicate balance presidents must

strike while participating in international efforts to

address global issues. See Curtiss-Wright, 299 U.S. at

319 (recognizing that in the “vast external realm [of

foreign affairs], with its important, complicated,

18

delicate, and manifold problems, the President alone

has the power to speak or listen as a representative of

the nation”).

The 1992 Earth Summit led to the Rio Declaration,

which included yet another commitment that the international community would develop “international

law regarding liability and compensation for adverse

effects” on the environment “caused by activities

within [a nation’s] jurisdiction or control to areas beyond their jurisdiction.” United Nations, Report of the

United Nations Conference on Environment and Development, Vol. I, at 5 (June 13, 1992), tinyurl.com/RioDec (Principle 13). Following the Earth Summit, the

United Nations established the UNFCCC, a forum for

international collaboration with which presidents

have occasionally had uneasy relationships (even

without the added complication of an intermeddling

state impairing the ability of the President to speak

clearly and decisively for the country).7

In the late 1990s, President Clinton was charged

with responding to a signature UNFCCC effort, the

Kyoto Protocol. Although President Clinton never presented the Kyoto Protocol for Senate ratification, and

so it never received the federal government’s full imprimatur, he directed Vice President Al Gore to sign it

on the United States’ behalf. The Clinton administration, moreover, shaped the Protocol’s substance in negotiations over its terms. 162 Cong. Rec. S1886 (daily

ed. Apr. 12, 2016) (statement of Sen. Inhofe) (noting

Clinton and Gore’s influence on the Kyoto Protocol).

7 See, e.g., Withdrawing the United States from International Or-

ganizations, Conventions, and Treaties that Are Contrary to the

Interests of the United States (Jan. 7, 2026), https://tinyurl.com/TrumpUNFCCC (ordering “all executive departments

and agencies . . . to take immediate steps to effectuate the withdrawal of the United States from” the UNFCCC).

19

Years later, President Bush took a different approach to the Kyoto Protocol. Consistent with the Senate’s opposition—expressed in the 1997 Byrd-Hagel

resolution,—to treaties that exempted major emitters

and threatened the United States’ economy’s prosperity, see infra Part III.2, President Bush announced

early in his Presidency that the United States would

not ratify, implement, or endorse the Kyoto Protocol.

In remarks explaining that decision, President Bush

alluded to the foreign affairs challenges presented by

emissions, including the need to hold nations like

China accountable for the emissions they produce and

the vital importance of “work[ing] cooperatively” with

other nations “to reduce greenhouse emissions and

maintain economic growth.” George W. Bush, President Bush Discusses Global Climate Change (June 11,

2001), https://tinyurl.com/BushOnClimate.

President Obama’s approach placed the United

States at the forefront of coordinating a global response to worldwide emissions. In a 2013 speech at

Georgetown University that announced his “national”

plan to combat greenhouse gas emissions, President

Obama proclaimed that “no nation can solve this challenge alone,” that the United States should “lead international efforts to combat” excessive emissions, and

that because the international community “looks to

America to lead” on this issue and many others, his

administration would “redouble [its] efforts” to

“reach[] a new global agreement” to reduce greenhouse

gas emissions. Barack Obama, Remarks by the President on Climate Change, (June 25, 2013), tinyurl.com/ObamaGeorgetown (emphasis added). He

further acknowledged that, although American emissions had decreased during the preceding year, global

emissions had risen to an all-time high—owing in

large part to “[d]eveloping nations,” including

20

“China—the world’s largest emitter,” continuing to use

“more and more energy.” Id. He therefore called for

other nations to “step[ ] up to the plate as well,” and

highlighted an “important agreement” with President

Xi of China,8 which marked a “significant step in the

reduction of carbon emissions” globally. Id.

President Biden took a similar approach. The Biden

administration recognized the need for the United

States to drive the global body politic toward sensible

approaches to balancing the need for reliable energy

production with the efforts to limit unnecessary greenhouse gas emissions. When conflict broke out in

Ukraine, the Biden administration acted swiftly to

preserve the United States’ ability to meet its own energy needs, as well as those of our allies, in the face of

disruptions to traditional global supply chains. See,

e.g., Joseph R. Biden & Ursula von der Leyen, Joint

Statement by President Biden and President Ursula

von der Leyen of the European Commission on European Energy Security (June 27, 2022), https://tinyurl.com/BidenOnEnergy (noting Russian efforts to

use “natural gas as a political and economic weapon”

had “threatened global energy security”). President

Biden promoted increased “U.S. [liquefied natural gas

(“LNG”)] exports to Europe,” which had “nearly tripled” since 2021, and which he said were vital to enabling Europe and the United States to “end [their] reliance on Russian energy.”

President Trump, both during his first term and

through his current administration, has taken forceful

action designed to ensure that all nations can reduce

8 President Obama was referring to an agreement to “phase down

the production and consumption” of certain products covered by

the Montreal Protocol. See United States and China Reach Agreement on Phase Down of HFCs (Sept. 6, 2013), https://tinyurl.com/ObamaOnCFCs.

21

their reliance energy from countries like Russia and

China and instead turn toward the United States.

Just last month, the Department of Energy announced

a key Memorandum of Understanding related to the

“Trump Peace Pipeline Framework” designed to continue to demonstrate that the United States is “a reliable partner” for nations aiming to “strengthen[ ] energy security.” U.S. Dep’t of Energy, Secretary Wright

Signs Agreements To Grow American LNG Exports,

Advances ‘Trump Peace Pipelines Framework’ (Apr.

28, 2026), https://tinyurl.com/TrumpPeacePipelines.

President Trump has also negotiated a host of trade

deals that demonstrate his foreign policy objective of

increasing energy production. For instance, he has obtained pledges from nations around the world committing those nations to purchase substantial quantities

of LNG from American manufacturers, thereby decreasing other nations’ reliance on the United States’

adversaries to meet their energy needs. See, e.g., U.S.

Dep’t of Energy, ICYMI: Energy Secretary Chris

Wright Delivers Remarks in Riyadh Following U.S.Saudi Energy Cooperation MOU Announcement, (Apr.

15, 2025), https://tinyurl.com/TrumpSaudiMOU (noting the United States and Kingdom of Saudi Arabia’s

agreement to “work together in cooperation” to increase global energy production). Such commitments

are vital to foreign trade policy, the national defense,

and preserving and promoting multilateral coordination.

In sum, the actions of presidents across the last several decades have left no doubt that the Executive

Branch understands that global greenhouse emissions

are a foreign affairs issue that demands a global solution. To lead the world rather than follow it, the “sole

organ” of the nation’s foreign affairs authority must retain the flexibility to promulgate and execute uniform

22

national policy developed by the federal government in

response to dynamic global conditions.

2. Congressional Action. Congress has also taken an

active role in directing the United States’ response to

issues related to global greenhouse gas emissions. The

United States Senate did not sit idly by, for instance,

while President Clinton shaped negotiations over the

Kyoto Protocol in 1997. Rather, with astonishing 95-0

unanimity, the Senate passed the Byrd-Hagel Resolution, which categorically opposed any treaty that

would exempt “Developing” nations—China among

them—from binding commitments to reduce greenhouse gas emissions or that would have a deleterious

effect on the United States economy. S. Res. 98, 105th

Cong. (1997). The Senate’s action sent a clear message: Any foreign-policy efforts that would let other

countries off the hook for their share of emissions was

dead on arrival. Just years before, the Senate had approved of the UNFCCC as a mechanism for addressing

the problem of global emissions. Id. But once the Senate determined that its proposal for doing so was “inconsistent with the need for global action” to check

greenhouse gas emissions, it was quick to express its

disapproval. Id. (emphasis added).

The Clean Air Act similarly demonstrates that Congress’s role in shaping the federal government’s response to regulations targeting greenhouse gas emissions leaves no room for contrary state opinion. In the

Act, Congress categorically forbade “State[s] or any political subdivision thereof” from “adopt[ing] or attempt[ing] to enforce any standard relating to the control of [vehicle] emissions,” 42 U.S.C. § 7543(a), unless

the EPA administrator issues the state a waiver after

determining that any state effort is consistent with

“Federal standards,” id. § 7543(b). Although California has received many such waivers and Congress has

23

permitted other states to adopt efforts identical to

those it has approved in parallel, the Act is clear that

State efforts to regulate emissions are permissible only

if they receive federal approval. See Benjamin M. Barczewski, Kathryn G. Kynett & Emily N. Peterson,

CONG. RSCH. SERV., R48168, California and the Clean

Air Act (CAA) Waiver: Frequently Asked Questions

(2025), https://tinyurl.com/CAAWaiverCRS.

More recently, Congress has supported presidential

efforts to promote domestic energy production and signal to international partners that the United States

can be counted on to assist nations that need to scale

up energy consumption. In the One Big Beautiful Bill

Act, for example, Congress established the Energy

Dominance Financing Program to guarantee loans for

projects that “secure [and] strengthen American energy assets,” see U.S. Dep’t of Energy, Office of Energy

Dominance Financing, tinyurl.com/DOEEDF (last visited May 13, 2026), and rolled back regulations that

unduly restrict domestic producers from meeting the

nation’s energy needs and those of our international

partners. See U.S. Dep’t of the Interior, Interior Dep’t

Advances Energy Dominance Through the One Big

Beautiful Bill Act, (July 22, 2025), https://tinyurl.com/DOIEnergyDominance (announcing the Department will implement “key changes” made by the

One Big Beautiful Bill Act to “promote U.S. energy

production”).

IV. STATE LAWS REGULATING U.S. COMPANIES’ ALLEGED CONTRIBUTIONS TO

GLOBAL EMISSIONS INTERFERE WITH

THE FEDERAL GOVERNMENT’S CONDUCT OF FOREIGN RELATIONS.

State laws that regulate the alleged contribution of

global greenhouse emissions by domestic energy companies—like the Colorado laws here—interfere with

24

the federal government’s express foreign policy and

conduct of foreign relations and thus are preempted.

As the decision below recognizes, Boulder’s suit under state law “presents substantial issues of global import,” seeking damages (and other remedies) “for the

role that [petitioners’] production, promotion, refining,

marketing, and sale of fossil fuels has allegedly played

in exacerbating climate change.” Pet. App. 1a-2a. Indeed, Boulder seeks damages for the allegedly “substantial role” petitioners play “in causing, contributing

to and exacerbating alteration of the climate.” Id. at

2a; see id. (alleging that petitioners “have caused and

continue to cause climate change”). A suit that targets

an oil-and-gas company (or set of companies) for the

alleged “role” that company “played in exacerbating

climate change” plainly seeks to hold that company liable for its alleged role in producing greenhouse gas

emissions and contributing to global climate change.

Id.; see City of New York v. Chevron, 993 F.3d 81, 91

(2d Cir. 2021) (“Artful pleading cannot transform

the … complaint into anything other than a suit over

global [GHG] emissions. It is precisely because fossil

fuels emit [GHGs]—which collectively ‘exacerbate

global warming’—that the City is seeking damages.”)

(emphasis original, citation omitted).

This state-law regime plainly “interferes with the

National Government’s conduct of foreign relations”

related to global greenhouse gas emissions and global

climate change, including the express foreign policy—

embodied in presidential and congressional actions

across decades—that addressing issues related to the

effects of global greenhouse gas emissions must be

handled on the world’s stage by working with foreign

nations. Garamendi, 539 U.S. at 401. The physical

mechanism that is allegedly injuring Boulder—the

prevalence of greenhouse gases in Earth’s

25

atmosphere—is a global one that is caused by everyone’s emissions everywhere on the planet. And Boulder’s suit seeks damages not for emissions that have

occurred in Colorado, but for the worldwide emissions

of particular companies in relation to all emissions

that have historically occurred globally.

Allowing state court juries to determine what share

of global climate change each American company

should be held responsible for impairs the President’s

“capacity to present a coherent position on behalf of”

the [Nation], thereby “weaken[ing]” the United States’

ability to “work[ ] together with other nations in hopes

of reaching common policy and ‘comprehensive’ strategy” to address greenhouse gases and global climate

change. Crosby, 530 U.S. at 381-82 (citation omitted).

The President’s power to persuade on the world’s stage

“rests on his capacity to bargain” on behalf of the entire nation “without exception[s] for” states engaging

in “inconsistent political tactics,” including state lawsuits—no matter whether dressed in the garb of tort,

nuisance, consumer protection, or antitrust—that seek

damages for energy companies’ supposed contributions to global climate change. Id. at 381.

At no point during Amici’s tenure in office did federal

interests in foreign policy yield to those of individual

states. Credibility is key to international negotiations,

especially on the issue of global greenhouse gas emissions, and the United States’ credibility is critically

damaged by State lawsuits that “undermine the President’s capacity” for “effective diplomacy” on this critical foreign affairs issue. Id. Colorado’s laws and other

state laws like them thus “compromis[e] the very capacity of the President to speak for the Nation with one

voice in dealing with other governments” in conducting

foreign affairs. Garamendi, 539 U.S. at 424 (quoting

Crosby, 530 U.S. at 381).

26

At bottom, the Constitution—its text, structure, and

history—entrust power over foreign affairs exclusively

in the federal government. When state law is likely to

produce “something more than incidental effect in conflict with express foreign policy of the National Government,” the Constitution “require[s] preemption of

the state law.” Id. at 420. Boulder’s suit seeking damages for allegedly “exacerbating climate change,” Pet.

App. 1a-2a, flunks this test, “weaken[s]” the United

States’ ability to “work[ ] together with other nations

in hopes of reaching common policy and [a] ‘comprehensive’ strategy” to address the effects of greenhouse

gas emissions and global climate change, Crosby, 530

U.S. at 381-82 (quoting Dames & Moore v. Regan, 453

U.S. 654, 673-74 (1981)), and is preempted.

27

CONCLUSION

For the foregoing reasons, the decision below should

be reversed.

Respectfully submitted,

WILLIAM P. BARR

CODY L. REAVES*

L. PATRICK ELLIS II

TORRIDON LAW PLLC

801 17th Street, NW

Suite 1100

Washington, D.C. 20006

(202) 249-6900

creaves@torridonlaw.com

Counsel for Amici Curiae

May 21, 2026

* Counsel of Record