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 AMICUS CURIAE

CTIA—THE WIRELESS ASSOCIATION

IN SUPPORT OF PETITIONERS

Thomas M. Johnson, Jr.

Counsel of Record

Joel S. Nolette

Brandon Beck

WILEY REIN LLP

2050 M Street NW

Washington, DC 20036

(202) 719-7000

tmjohnson@wiley.law

May 21, 2026

Counsel for Amicus Curiae

i

TABLE OF CONTENTS

TABLE OF CONTENTS ............................................. i

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

INTEREST OF AMICUS CURIAE ............................1

INTRODUCTION AND SUMMARY OF

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

ARGUMENT ...............................................................7

I.

The Presumption Against Preemption Should

Not Apply Where, as Here, the Regulatory

Field Is Traditionally Federal.........................7

A. The Constitution’s Structure Militates

Against Applying the Presumption in

This Context. ............................................7

B. The Field of Interstate Communications

Illustrates Why the Presumption Should

Not Apply to Primarily Interstate

Activities. ................................................16

II. Applying the Presumption Against

Preemption in Traditionally Federal Fields

Exacerbates the Very Problems That the

Constitution’s Structure Is Meant to

Ameliorate. ....................................................19

CONCLUSION ..........................................................23

ii

TABLE OF AUTHORITIES

Page(s)

Cases

ACA Connects v. Bonta,

24 F.4th 1233 (9th Cir. 2022) ............. 2, 5, 21–22

Allen B. Dumont Lab’ys v. Carroll,

184 F.2d 153 (3d Cir. 1950) .............................. 18

Am. Elec. Power Co. v. Connecticut,

564 U.S. 410 (2011) ........................................... 15

Am. Legion v. Am. Humanist Ass’n,

588 U.S. 29 (2019) ............................................. 13

AT&T Mobility L.L.C. v. Concepcion,

563 U.S. 333 (2011) ............................................. 1

Baldwin v. G.A.F. Seelig, Inc.,

294 U.S. 511 (1935) ........................................... 19

Missouri ex rel. Barrett v. Kan. Nat. Gas

Co.,

265 U.S. 298 (1924) ....................................... 5, 17

Biden v. Nebraska,

600 U.S. 477 (2023) ............................................. 6

BMW of N. Am., Inc. v. Gore,

517 U.S. 559 (1996) ........................................... 20

Buckman Co. v. Pls.’ Legal Comm.,

531 U.S. 341 (2001) ..................................... 16, 19

iii

C & A Carbone, Inc. v. Town of Clarkstown,

511 U.S. 383 (1994) ........................................... 19

Camps Newfound/Owatonna, Inc. v. Town

of Harrison,

520 U.S. 564 (1997) ........................................... 11

City & Cnty. of Honolulu v. Sunoco LP,

537 P.3d 1173 (Haw. 2023) ................................. 7

City of Arlington v. FCC,

569 U.S. 290 (2013) ............................................. 1

City of Milwaukee v. Illinois,

451 U.S. 304 (1981) ........................................... 15

City of New York v. Chevron Corp.,

993 F.3d 81 (2d Cir. 2021) .................. 4, 7, 15, 21

Crosby v. Nat’l Foreign Trade Council,

530 U.S. 363 (2000) ........................................... 16

Cummings v. Missouri,

71 U.S. (4 Wall.) 277 (1866) .............................. 20

Elkison v. Deliesseline,

8 F. Cas. 493 (C.C.D.S.C. 1823) ........................ 12

FCC v. AT&T, Inc.,

No. 25-406 (U.S. argued Apr. 21, 2026) ............. 1

First Choice Women’s Res. Ctrs., Inc. v.

Davenport,

608 U.S. ----, 2026 WL 1153029 (2026) ............ 20

Franchise Tax Bd. of Cal. v. Hyatt,

587 U.S. 230 (2019) ........................................... 20

iv

FRC v. Nelson Bros. Bond & Mortg. Co.,

289 U.S. 266 (1933) ........................................... 18

Gibbons v. Ogden,

22 U.S. (9 Wheat.) 1 (1824) ....................... 3, 8, 12

Gonzales v. Raich,

545 U.S. 1 (2005) ............................................... 13

H.P. Hood & Sons, Inc. v. Du Mond,

336 U.S. 525 (1949) ....................................... 9, 12

Illinois v. City of Milwaukee,

406 U.S. 91 (1972) ............................................. 15

Illinois v. City of Milwaukee,

731 F.2d 403 (7th Cir. 1984) ............................. 22

Int’l Paper Co. v. Ouellette,

479 U.S. 481 (1987) ............. 3, 6–7, 16, 19, 22–23

Int’l Text-Book Co. v. Pigg,

217 U.S. 91 (1910) ............................................. 12

Ivy Broad. Co. v. Am. Tel. & Tel. Co.,

391 F.2d 486 (2d Cir. 1968) .............................. 18

Kansas v. Colorado,

206 U.S. 46 (1907) ....................................... 20, 22

La. Pub. Serv. Comm’n v. FCC,

476 U.S. 355 (1986) ........................................... 18

Leisy v. Hardin,

135 U.S. 100 (1890) ................................. 5, 17, 19

v

Limelight Networks, Inc. v. Akamai Techs.,

Inc.,

572 U.S. 915 (2014) ............................................. 1

Loper Bright Enters. v. Raimondo,

603 U.S. 369 (2024) ............................................. 2

Mayor & City Council of Balt. v. B.P. P.L.C.,

353 A.3d 1142 (Md. 2026) ................................. 15

Mayor, Aldermen & Commonalty of City of

N.Y. v. Miln,

36 U.S. (11 Pet.) 102 (1837) .............................. 13

McLeod v. J.E. Dilworth Co.,

322 U.S. 327 (1944) ........................................... 11

Mobile County v. Kimball,

102 U.S. 691 (1880) ........................................... 11

Murphy v. NCAA,

584 U.S. 453 (2018) ............................................. 8

N.Y. State Rifle & Pistol Ass’n v. Bruen,

597 U.S. 1 (2022) ............................................... 13

N.Y. State Telecomms. Ass’n v. James,

101 F.4th 135 (2d Cir. 2024) ..................... 2, 5, 21

Nat’l Pork Producers Council v. Ross,

598 U.S. 356 (2023) ..................................... 14, 22

New Prime Inc. v. Oliveira,

586 U.S. 105 (2019) ........................................... 14

vi

Or. Waste Sys., Inc. v. Dep’t of Env’t Quality

of State of Or.,

511 U.S. 93 (1994) ............................................. 13

Pennsylvania v. West Virginia,

262 U.S. 553 (1923) ........................................... 19

Pike v. Bruce Church, Inc.,

397 U.S. 137 (1970) ............................... 13–14, 22

Postal Tel.-Cable Co. v. Warren-Godwin

Lumber Co.,

251 U.S. 27 (1919) ............................................. 17

Quill Corp. v. North Dakota ex rel.

Heitkamp,

504 U.S. 298 (1992) ........................................... 13

R.R. Co. v. Husen,

95 U.S. 465 (1877) ............................................. 12

Rhode Island v. Massachusetts,

37 U.S. (12 Pet.) 657 (1838) ................................ 8

Rice v. Santa Fe Elevator Corp.,

331 U.S. 218 (1947) ................................... 2, 8, 14

S. Pac. Co. v. Arizona ex rel. Sullivan,

325 U.S. 761 (1945) ........................................... 12

United States ex rel. Schutte v. Supervalu

Inc.,

598 U.S. 739 (2023) ............................................. 1

Seila Law LLC v. CFPB,

591 U.S. 197 (2020) ............................................. 8

vii

Shelby County v. Holder,

570 U.S. 529 (2013) ........................................... 20

South Dakota v. Wayfair,

585 U.S. 162 (2018) ........................................... 13

Sprint Commc’ns, Inc. v. Jacobs,

571 U.S. 69 (2013) ............................................... 1

T-Mobile S., L.L.C. v. City of Roswell,

574 U.S. 293 (2015) ............................................. 1

TRW Inc. v. Andrews,

534 U.S. 19 (2001) ............................................. 14

United States v. E.C. Knight Co.,

156 U.S. 1 (1895) ............................................... 16

United States v. Locke,

529 U.S. 89 (2000) ..................................... 3, 8, 16

United States v. Rahimi,

602 U.S. 680 (2024) ........................................... 13

Universal Health Servs., Inc. v. United

States ex rel. Escobar,

579 U.S. 176 (2016) ............................................. 1

W. Union Tel. Co. v. Boegli,

251 U.S. 315 (1920) ........................................... 17

Wabash, St. Louis & Peoria Ry. Co. v.

Illinois,

118 U.S. 557 (1886) ........................................... 16

Wis. Bell, Inc. v. United States ex rel. Heath,

604 U.S. 140 (2025) ............................................. 1

viii

Constitutional Provisions

U.S. Const. art. I, § 8, cl. 3 ................................... 3, 8

Statutes

47 U.S.C. § 152 ............................................... 2, 4, 18

Mann-Elkins Act, Pub. L. No. 61-218, 36

Stat. 539 (1910) ................................................. 17

Radio Act of 1912, Pub. L. No. 62-264, 37

Stat. 302 (1912) ................................................. 18

Radio Act of 1927, Pub. L. No. 69-632, 44

Stat. 1162 (1927) ............................................... 18

Other Materials

Barry Friedman & Daniel T. Deacon, A

Course Unbroken: The Constitutional

Legitimacy of the Dormant Commerce

Clause, 97 Va. L. Rev. 1877 (2011) ............. 10, 12

David S. Day, Revisiting Pike: The Origins

of the Nondiscrimination Tier of the

Dormant Commerce Clause Doctrine, 27

Hamline L. Rev. 45 (2004) ................................ 13

Elliot, The Debates in the Several State

Conventions (1836) ........................................ 9, 11

Federal Farmer No. 6 (1787) .................................. 10

The Federalist No. 7 ................................................. 9

The Federalist No. 11 ............................................... 9

ix

The Federalist No. 14 ............................................. 11

The Federalist No. 22 ......................................... 9–10

The Federalist No. 42 ............................................. 19

M. Farrand, Records of the Federal

Convention of 1787 (1911) ................................ 11

Peter S. Onuf & Cathy Matson,

Republicanism & Federalism in the

Constitutional Decade, 102 Am.

Antiquarian Soc’y 181 (1992) ........................... 10

Viet D. Dinh, Reassessing the Law of

Preemption, 88 Geo. L.J. 2085 (2000)............... 16

1

INTEREST OF AMICUS CURIAE1

CTIA—The Wireless Association represents the

U.S. wireless communications industry and the companies throughout the mobile ecosystem that enable

Americans to lead a 21st-century connected life, including wireless providers, device manufacturers,

suppliers, as well as application and content companies. CTIA regularly files amicus briefs in cases presenting issues of importance to its members. See, e.g.,

FCC v. AT&T, Inc., No. 25-406 (U.S. argued Apr. 21,

2026); Wis. Bell, Inc. v. United States ex rel. Heath,

604 U.S. 140 (2025); United States ex rel. Schutte v.

Supervalu Inc., 598 U.S. 739 (2023); Universal Health

Servs., Inc. v. United States ex rel. Escobar, 579 U.S.

176 (2016); T-Mobile S., L.L.C. v. City of Roswell, 574

U.S. 293 (2015); Limelight Networks, Inc. v. Akamai

Techs., Inc., 572 U.S. 915 (2014); Sprint Commc’ns,

Inc. v. Jacobs, 571 U.S. 69 (2013); City of Arlington v.

FCC, 569 U.S. 290 (2013); AT&T Mobility L.L.C. v.

Concepcion, 563 U.S. 333 (2011).

CTIA’s members frequently face attempts by

states to regulate their interstate activities. Because

CTIA’s members operate national, interstate networks, state-level regulation of network operations

can require nationwide engineering or process

changes, imposing significant compliance costs and

encouraging a “race to the bottom” where the most

burdensome state rules become a de facto nationwide

standard. Those regulations are—or at least should

1 No party’s counsel authored this brief in whole or in part, and

no person or entity other than Amicus Curiae, its members, or

its counsel made a monetary contribution to fund the brief’s preparation or submission.

2

be—preempted under the Communications Act. See,

e.g., 47 U.S.C. § 152(a) (“The provisions of this chapter

shall apply to all interstate . . . communication by wire

or radio . . . .”). But too often, courts have wrongly

held otherwise. See, e.g., N.Y. State Telecomms. Ass’n

v. James, 101 F.4th 135 (2d Cir. 2024); ACA Connects

v. Bonta, 24 F.4th 1233 (9th Cir. 2022). Thus, CTIA

has a strong interest in how the Court explains

preemption in this dispute involving the interstate activities of Suncor Energy and Exxon Mobil.

INTRODUCTION AND

SUMMARY OF ARGUMENT

This Court recently vindicated the structural separation of powers between Congress and the Executive Branch by instructing federal courts to identify

the “best reading” of a statute, rather than defer to

strained, contestable readings by government agencies. Loper Bright Enters. v. Raimondo, 603 U.S. 369,

400 (2024). That principle of giving controlling effect

to congressional intent—embodied in the text of the

laws it enacts, interpreted according to the text’s

meaning at the time of enactment, id.—is no less important to vindicate the vertical separation of powers

between the federal government and the States.

This Court has sometimes applied a presumption

against preemption of state and local laws when Congress legislates “in [a] field which the States have traditionally occupied,” within the States’ “historic police

powers.” Rice v. Santa Fe Elevator Corp., 331 U.S. 218,

230 (1947). But for as long as that presumption has

existed, this Court has also recognized that it is “not

triggered when [a] State regulates in an area where

there has been a history of significant federal

3

presence.” United States v. Locke, 529 U.S. 89, 108

(2000) (discussing Rice, 331 U.S. at 230). To the contrary, in such areas that have traditionally been “primarily a matter of federal law,” “it may be presumed”

that there is “no room for supplementary state regulation” and that the only permissible state-law actions

are those “specifically preserved by the Act” of Congress at issue. Int’l Paper Co. v. Ouellette, 479 U.S. 481,

491–92 (1987) (cleaned up).

That distinction between areas historically regulated at the federal level and those within the States’

traditional police powers vindicates a core constitutional principle dating back to the Founding—that the

federal government, not the States, had the exclusive

authority to regulate in the areas of foreign or interstate commerce. U.S. Const. art. I, § 8, cl. 3; Gibbons

v. Ogden, 22 U.S. (9 Wheat.) 1, 209 (1824) (Marshall,

C.J.). While this Court’s Commerce Clause jurisprudence has evolved over time, this traditional understanding of the division of federal and state power informed how Congress understood the limited role it

was assigning to States under a number of complex,

federal regulatory statutes governing primarily interstate activities.

In the Communications Act of 1934 that regulates

CTIA’s members’ interstate communications networks and services, for example, careful attention to

text, structure, and contemporaneous history show

that Congress intended for States to regulate only local, intrastate activity. But in the decision below (and

in several recent Communications Act cases), courts

have uncritically applied a presumption against

preemption to allow States to regulate concededly

4

interstate activities—contrary to constitutional and

congressional design.

This case involves an area that this Court considered to be inherently national in character and that

for over a hundred years had been governed by principles of federal common law. Pet. 22.2 When Congress

displaced that common law with a comprehensive federal regulatory scheme, some courts correctly concluded that this enactment did not “suddenly” make

state law “presumptively competent” to regulate interstate activities but merely replaced “a federal

court-made standard with a legislative one.” City of

New York v. Chevron Corp., 993 F.3d 81, 98 (2d Cir.

2021). But the Colorado Supreme Court below

wrongly concluded that replacing federal common law

with statutory law meant that fifty States could each

regulate inherently national activity unless a court

could locate “clear and manifest purpose” to “supersede[]” state law. Pet. App. 11a (applying the presumption against preemption).

The Communications Act provides a similar case

study. Section 2 of the Act provides that the federal

government has jurisdiction over interstate communications, on one hand, and States have jurisdiction over

intrastate communications, on the other. See 47 U.S.C.

§ 152. Congress borrowed this language originally

from the late-nineteenth century Interstate Commerce Act, adopted at a time when courts still embraced the Founding-era view that States could not

regulate interstate activities unless Congress

2 CTIA’s members take no position on the underlying environ-

mental policy issues implicated by the federal and state laws at

issue in this case.

5

authorized them to do so. Leisy v. Hardin, 135 U.S.

100, 108 (1890). In that era, reflecting the original

constitutional design, congressional “silence” on an issue was “equivalent to a declaration that that particular commerce shall be free from regulation.” Missouri ex rel. Barrett v. Kan. Nat. Gas Co., 265 U.S. 298,

308 (1924).

Nonetheless, the absence of modern-day express

preemption language in Section 2 of the Act has led

courts wrongly to conclude that States may regulate

even admittedly interstate services—such as the entire, end-to-end national broadband Internet network—through invoking a presumption against

preemption or its equivalent. For example, the Ninth

Circuit has reasoned that absent “express preemption”

language in the Act, States “otherwise . . . have concurrent authority to regulate interstate services.”

ACA Connects, 24 F.4th at 1248. Similarly, the Second

Circuit has concluded that the “absence of regulation”

under the Communications Act means that Congress

did not intend to preempt the field with respect to interstate broadband networks. N.Y. State Telecomms.

Ass’n, 101 F.4th at 152.

The result of the misapplication of the presumption against preemption in cases like these, contrary

to what Congress and the Constitution envision, can

be devastating for providers of critical interstate communications services. Because communications network architecture and engineering often transcend

state lines—as do the many phone calls, emails, text

messages, and other communications that connect

people nationwide—it can be impracticable if not impossible for providers to apply one set of technical

6

standards in California and another in Kansas. Rather than comply with a single, national set of regulations that reflect input from stakeholders across the

country, providers often have to default to the most

restrictive State’s standards (which are ever-shifting).

The result is significant regulatory cost and uncertainty, and damage to the constitutional structure, as

regulators in Sacramento, Albany, or other state capitals can effectively impose nationwide standards on

interstate commerce.

The Court should make clear that the presumption

against preemption does not apply to state laws in traditionally federal fields like the one at issue in this

case and that, if anything, preemption should be “presumed” in such “primarily . . . federal” areas. Ouellette,

479 U.S. at 491–92; cf. Biden v. Nebraska, 600 U.S.

477, 511–16 (2023) (Barrett, J., concurring) (explaining that interpretive presumptions are valid to the extent they function as a textual “interpretive tool reflecting common sense as to the manner in which Congress is likely” to legislate in light of background constitutional, legal, and historical contexts (cleaned up)).

7

ARGUMENT

I.

The Presumption Against Preemption

Should Not Apply Where, as Here, the Regulatory Field Is Traditionally Federal.

A.

The Constitution’s Structure Militates Against Applying the Presumption in This Context.

In holding that federal law did not preempt the

state-law claims of the County Commissioners of

Boulder County and the City of Boulder (collectively,

“Boulder”) against Suncor Energy and Exxon Mobil,

the Colorado Supreme Court put a thumb on the analytical scale in favor of Boulder by applying the “presumption against preemption.” Pet. App. 11a–12a.

And other courts have done the same in related cases.

See, e.g., City & Cnty. of Honolulu v. Sunoco LP, 537

P.3d 1173, 1203 (Haw. 2023) (“Courts begin with the

presumption that state laws and claims are not

preempted.”). But in cases like this involving “an area

traditionally governed by federal law,” Pet. App. 36a

(Samour, J., dissenting), the presumption against

preemption should not apply. To the contrary, if anything, in these areas preemption may be “presumed,”

Ouellette, 479 U.S. at 491, and the question is

“whether federal law ‘authorizes resort to state law,’”

Pet. App. 35a (Samour, J., dissenting) (quoting Illinois v. City of Milwaukee, 731 F.2d 403, 410 (7th Cir.

1984) (“Milwaukee III”)); accord Chevron Corp., 993

F.3d at 99 (citing, inter alia, Ouellette, 479 U.S. at 492).

This conclusion follows from first principles. The

Court created the presumption against preemption to

guard against permitting inadvertent federal

8

encroachment into the “historic police powers of the

States.” Rice, 331 U.S. at 230. But under the Constitution’s structure, not every regulatory domain falls

under the auspices of the States’ “historic police powers.” Id.; see, e.g., Locke, 529 U.S. at 108 (discussing

the field of “national and international maritime commerce” in which “there is no beginning assumption

that concurrent regulation by the State is a valid exercise of its police powers”). After all, the Constitution

deliberately “split the atom of sovereignty itself into

one Federal Government and the States.” Seila Law

LLC v. CFPB, 591 U.S. 197, 223 (2020) (cleaned up).

And in doing so, the Framers allocated authority over

certain fields to the federal government, removing

that authority in turn from the domain of the States’

police power. See Rhode Island v. Massachusetts, 37

U.S. (12 Pet.) 657, 720 (1838) (under the Constitution,

States are “sovereign within their respective boundaries, save that portion of power which they have

granted to the federal government”).

In other words, the “Constitution limits state sovereignty in several ways,” both “directly” and “implicit[ly].” Murphy v. NCAA, 584 U.S. 453, 470 (2018)

(citing, inter alia, Dep’t of Revenue of Ky. v. Davis, 553

U.S. 328 (2008)). And as relevant here, one prominent

way in which the Constitution did so was by committing the field of interstate commerce to Congress. See

U.S. Const. art. I, § 8, cl. 3.

Rectifying the commercial relations among the

States—or lack thereof—under the Articles of Confederation was the main impetus for the Constitutional

Convention. Gibbons, 22 U.S. (9 Wheat.) at 224 (Johnson, J., concurring in the judgment) (the “immediate

9

cause, that led to the forming of a convention,” was “a

conflict of commercial regulations, destructive to the

harmony of the States”). As Alexander Hamilton observed, some States had adopted “interfering and unneighborly regulations” that were “contrary to the

true spirit of the Union” that, “if not restrained by a

national control, would be multiplied and extended” to

the ultimate demise of the Nation. The Federalist No.

22 (Alexander Hamilton); accord The Federalist No. 7

(Alexander Hamilton) (expressing the dangers of each

State pursuing “a system of commercial policy peculiar to itself”).

So apparent was the need for a “unity of government” in the field of interstate commerce, The Federalist No. 11 (Alexander Hamilton), that members of

the founding generation spanning the ideological

spectrum were essentially of one accord in the view

that this power should belong to the national government, not the States. E.g., H.P. Hood & Sons, Inc. v.

Du Mond, 336 U.S. 525, 533–34 (1949) (explaining

that this “necessity” was “so obvious and so fully recognized” at the Constitutional Convention that “the

few words of the Commerce Clause were little illuminated by debate”); 3 Elliot, The Debates in the Several

State Conventions 260 (1836) (James Madison) (asserting in the Virginia ratification debates that “[a]ll

agree that the general government ought to have

power for the regulation of commerce” and that such

power would protect the Union against “interfering

regulations of different states”).

On one hand, Federalists of the day argued “that

‘nothing short of vesting Congress with full powers to

regulate the internal as well as the external commerce

10

of all the states, can reach the mischiefs’” then-plaguing the country. Peter S. Onuf & Cathy Matson, Republicanism & Federalism in the Constitutional Decade, 102 Am. Antiquarian Soc’y 181, 190–91 (1992)

(quoting Resolutions of the Merchants, Traders and

others of the town of Boston, April 22, 1785, Pennsylvania Gazette, June 8, 1785); see also Barry Friedman

& Daniel T. Deacon, A Course Unbroken: The Constitutional Legitimacy of the Dormant Commerce Clause,

97 Va. L. Rev. 1877, 1886 (2011) (discussing a pseudonymous piece by “Pro Bono Republicae” published

in the Pennsylvania Gazette around the same time,

which “call[ed] it ‘a very ridiculous idea, that every

State should enjoy a power of regulating its trade, for

every State has a separate interest to pursue, and

thus different regulations will always clash’”); cf. The

Federalist No. 22 (Alexander Hamilton) (identifying

the “gradual conflicts of State regulations” of commerce as an inherent threat to national unity).

On the other hand, though “the Anti-Federalists

objected to a great many things in the new Constitution,” “nary a peep was heard against the view that

the control over commerce in its foreign and interstate

aspects should be centralized.” Friedman & Deacon,

supra, at 1893–94; see also, e.g., Federal Farmer No. 6

(1787) (“The powers of the union ought to be extended

to commerce, the coin, and national objects . . . .”).

And those in the middle concurred. For instance,

at the Constitutional Convention James Madison explained that the “regulation of Commerce was in its

nature indivisible and ought to be wholly under one

authority” and that giving Congress the power to regulate interstate commerce would “exclude this power

11

of the States.” 2 M. Farrand, Records of the Federal

Convention of 1787, at 625 (1911); accord The Federalist No. 14 (James Madison) (“WE HAVE seen the

necessity of the Union . . . as the guardian of our commerce and other common interests . . . .”). And Robert

R. Livingston explained in the New York ratification

debates that the authority to regulate interstate commerce had to be allocated to the federal government

because “this power could never be trusted to the individual states, whose interests might, in many instances, clash with that of the Union.” 2 Elliot, supra,

at 214–15.

Accordingly, the Constitution vested in the new

federal “Congress the power to regulate commerce . . .

among the States” with a view to ensuring “uniformity

of regulation against conflicting and discriminating

State legislation.” Mobile County v. Kimball, 102 U.S.

691, 697 (1880); see also McLeod v. J.E. Dilworth Co.,

322 U.S. 327, 330 (1944) (“The very purpose of the

Commerce Clause was to create an area of free trade

among the several States.”). And this allocation of authority to the federal government not only “granted

Congress express authority to override restrictive and

conflicting commercial regulations adopted by the

States” but also inherently “effected a curtailment of

state power” of its own force. Camps Newfound/Owatonna, Inc. v. Town of Harrison, 520 U.S.

564, 571 (1997); see also, e.g., 1 Farrand, supra, at 416

(quoting James Wilson who placed “Commerce” alongside “War, Peace, [and] Treaties” as powers “peculiar”

to the federal government).

Leading federal jurists in the early post-ratification period recognized as much. For instance, while

12

riding circuit, President Jefferson’s first appointee to

this Court, Justice William Johnson, Jr., held that a

pro-slavery South Carolina law violated the Commerce Clause, reasoning in the process that the “unquestionable” and “universal construction” of the

Commerce Clause at the time was that it vested in the

“general government . . . a paramount and exclusive

right.” Elkison v. Deliesseline, 8 F. Cas. 493, 495

(C.C.D.S.C. 1823) (No. 4366). And soon thereafter, in

this Court’s “first extended discussion of the dormant

commerce power,” Friedman & Deacon, supra, at 1905,

Chief Justice Marshall spoke approvingly of the view

that the Commerce Clause gave “full power” over interstate commerce to the federal government, Gibbons,

22 U.S. (9 Wheat.) at 209 (opinion of Marshall, C.J.),

leaving “exclusively internal commerce” alone to the

States, id. at 195.

Subsequently, that understanding was “accepted

constitutional doctrine” for the better part of the Nation’s history. See S. Pac. Co. v. Arizona ex rel. Sullivan, 325 U.S. 761, 769 (1945); see also, e.g., H.P. Hood

& Sons, 336 U.S. at 535 (“[T]he right to engage in interstate commerce is not the gift of a state, and . . . a

state cannot regulate or restrain it.”); Int’l Text-Book

Co. v. Pigg, 217 U.S. 91, 112 (1910) (“It is the established doctrine of this court that a state may not, in

any form or under any guise, directly burden the prosecution of interstate business.”); R.R. Co. v. Husen, 95

U.S. 465, 471–72 (1877) (“[W]hatever may be the nature and reach of the police power of a State . . . . It

cannot invade the domain of the national government. . . . police powers[] can[not] be exercised to such

an extent as to work a practical assumption of the

powers properly conferred upon Congress by the

13

Constitution.”); cf. Mayor, Aldermen & Commonalty of

City of N.Y. v. Miln, 36 U.S. (11 Pet.) 102, 132 (1837)

(upholding a state law against a Commerce Clause

challenge on the basis that it was not “a regulation of

commerce, but of police”).

Granted, this Court’s Commerce Clause jurisprudence would eventually evolve substantially from that

traditional understanding. See, e.g., Gonzales v. Raich,

545 U.S. 1, 15–16 (2005) (“[O]ur understanding of the

reach of the Commerce Clause, as well as Congress’

assertion of authority thereunder, has evolved over

time.”); Quill Corp. v. North Dakota ex rel. Heitkamp,

504 U.S. 298, 309 (1992) (“Our interpretation of the

‘negative’ or ‘dormant’ Commerce Clause has evolved

substantially over the years . . . .”), overruled on other

grounds by South Dakota v. Wayfair, 585 U.S. 162

(2018).3 Even so, “[c]onsistent with these [first] principles,” Or. Waste Sys., Inc. v. Dep’t of Env’t Quality of

State of Or., 511 U.S. 93, 98–99 (1994) (citing, inter

alia, Pike v. Bruce Church, Inc., 397 U.S. 137, 142

(1970)), the Court has not abandoned this traditional

understanding (even if it has reworked how it applies).

See Pike, 397 U.S. at 142 (enunciating a “general rule”

out of prior dormant Commerce Clause cases); David

S. Day, Revisiting Pike: The Origins of the Nondiscrimination Tier of the Dormant Commerce Clause

3 But see N.Y. State Rifle & Pistol Ass’n v. Bruen, 597 U.S. 1, 28

(2022) (the Constitution’s “meaning is fixed according to the understandings of those who ratified it”); United States v. Rahimi,

602 U.S. 680, 737 (2024) (Barrett, J., concurring) (“the meaning

of constitutional text is fixed at the time of its ratification”); Am.

Legion v. Am. Humanist Ass’n, 588 U.S. 29, 87 (2019) (Gorsuch,

J., concurring in the judgment) (“The Constitution’s meaning is

fixed, not some good-for-this-day-only coupon . . . .”).

14

Doctrine, 27 Hamline L. Rev. 45, 46 (2004) (describing

Pike as a “conscious effort to synthesize” earlier

dormant Commerce Clause caselaw). Rightly so—as a

majority of this Court recently confirmed, “the Constitution the Framers adopted in Philadelphia in 1787”

demands nothing less. Nat’l Pork Producers Council v.

Ross, 598 U.S. 356, 407 & n.3 (2023) (Kavanaugh, J.,

concurring in part and dissenting in part); accord id.

at 395 (Roberts, C.J., concurring in part and dissenting in part) (“Today’s majority does not pull the plug

[on Pike]. For good reason: . . . it . . . reflects the basic

concern of our Commerce Clause jurisprudence that

there be ‘free private trade in the national marketplace.’” (quoting Gen. Motors Corp. v. Tracy, 519 U.S.

278, 287 (1997))).

In any event, this traditional understanding of the

division of federal and state power confirms that the

regulation of interstate activity is not within the ambit of the States’ “historic police powers.” Rice, 331 U.S.

at 230. Further, this traditional understanding

formed the backdrop against which Congress enacted

a number of complex regulatory statutes governing

primarily interstate activities. And those enactments

must be interpreted in light of that background understanding. See, e.g., New Prime Inc. v. Oliveira, 586

U.S. 105, 113 (2019) (“It is a fundamental canon of

statutory construction that words generally should be

interpreted as taking their ordinary . . . meaning . . .

at the time Congress enacted the statute.” (cleaned

up)); TRW Inc. v. Andrews, 534 U.S. 19, 38 (2001)

(Scalia, J., concurring in the judgment) (“To apply a

new background rule to previously enacted legislation

would reverse prior congressional judgments . . . .”).

15

That is the case here. Suncor Energy and Exxon

Mobil are alleged to have engaged in activities in a

field that has long been recognized to belong to the

federal government to regulate—the field of conduct

affecting “air and water in their ambient or interstate

aspects.” Illinois v. City of Milwaukee, 406 U.S. 91,

103, 105 n.6 (1972), abrogation on other grounds recognized by City of Milwaukee v. Illinois, 451 U.S. 304

(1981) (“Milwaukee II”); see also Milwaukee II, 451

U.S. at 313 n.7 (indicating that the Court had previously fashioned a federal-common-law rule of decision

in the case “because state law cannot be used” in that

field); Am. Elec. Power Co. v. Connecticut, 564 U.S.

410, 421 (2011) (“Environmental protection is undoubtedly an area within national legislative power,

one in which federal courts may fill in statutory interstices, and, if necessary, even fashion federal law.”

(cleaned up)); Chevron Corp., 993 F.3d at 91 (“For over

a century, a mostly unbroken string of cases has applied federal law to disputes involving interstate air

or water pollution.” (collecting authorities)).

Against this backdrop, Congress enacted the Clean

Air Act. In doing so, Congress “displace[d]” the previous “federal common-law” rules that courts had

crafted. Am. Elec. Power Co., 564 U.S. at 424. But

Congress did so “not in a field in which the states have

traditionally occupied, but one in which the states

have traditionally not occupied.” Chevron Corp., 993

F.3d at 98 (cleaned up); accord Mayor & City Council

of Balt. v. B.P. P.L.C., 353 A.3d 1142, 1171–76 (Md.

2026).

So “in contrast to situations implicating federalism

concerns and the historic primacy of state regulation,”

16

“no presumption against pre-emption obtains in this

case.” Buckman Co. v. Pls.’ Legal Comm., 531 U.S. 341,

348 (2001) (cleaned up); accord Locke, 529 U.S. at 108

(declining to apply this “artificial presumption” in

similar circumstances); cf. Viet D. Dinh, Reassessing

the Law of Preemption, 88 Geo. L.J. 2085, 2087 (2000)

(“[T]he constitutional structure of federalism does not

admit to a general presumption against federal

preemption of state law.”). To the contrary, preemption is implicit in the statute, and “the only state suits

that remain available are those specifically preserved”

by the Clean Air Act. Ouellette, 479 U.S. at 492; cf.

Crosby v. Nat’l Foreign Trade Council, 530 U.S. 363,

387–88 (2000) (“A failure to provide for preemption expressly may reflect nothing more than the settled

character of implied preemption doctrine that courts

will dependably apply . . . .”).

B.

The Field of Interstate Communications Illustrates Why the Presumption Should Not Apply to Primarily

Interstate Activities.

The field of interstate communications, in which

CTIA’s members operate, provides a helpful parallel

illustration for why the presumption against preemption does not apply—and, if anything, the converse

does—in this case.

In the form we know it today, the field of interstate

communications took shape in the late nineteenth

century. At that time, federal authority over the field

of interstate commerce generally was understood to be

“exclusive.” United States v. E.C. Knight Co., 156 U.S.

1, 11 (1895); accord Wabash, St. Louis & Peoria Ry.

Co. v. Illinois, 118 U.S. 557, 577 (1886) (regulations in

17

this field “must be, if established at all, of a general

and national character, and cannot be safely and

wisely remitted to local rules and local regulations”).

Per this traditional understanding, States had no “jurisdiction” to regulate in the field unless authorized to

do so by “congressional action.” Leisy, 135 U.S. at 108.

Otherwise, Congress’s “silence” was “equivalent to a

declaration that that particular commerce shall be

free from regulation.” Kan. Nat. Gas Co., 265 U.S. at

308.

Against this backdrop, Congress enacted the

Mann-Elkins Act, amending the Interstate Commerce

Act to give the Interstate Commerce Commission authority over “telegraph, telephone, and cable companies . . . engaged in sending messages from one

State . . . to any other State” (while leaving to States

the regulation of such messages transmitted “wholly

within one State”). Pub. L. No. 61-218, § 7, 36 Stat.

539, 544–45 (1910). As this Court recognized soon

thereafter, that jurisdictional allocation—tracking

the Court’s contemporary Commerce Clause jurisprudence—“was an exertion by Congress of its authority

to bring under federal control the interstate business

of telegraph companies and therefor was an occupation of the field by Congress which excluded state action.” Postal Tel.-Cable Co. v. Warren-Godwin Lumber

Co., 251 U.S. 27, 31 (1919); accord W. Union Tel. Co.

v. Boegli, 251 U.S. 315, 316 (1920) (holding that the

Mann-Elkins Act “so clearly establish[ed] the purpose

of Congress to subject such companies to a uniform

national rule as to cause it to be certain that there was

no room thereafter for the exercise by the several

states of power to regulate . . . an interstate telegram”).

18

Congress then carried that interstate-intrastate

jurisdictional allocation forward in the Radio Act of

1912, Pub. L. No. 62-264, § 1, 37 Stat. 302, 302 (1912);

in the Radio Act of 1927, Pub. L. No. 69-632, § 1, 44

Stat. 1162, 1162 (1927); and ultimately in the Communications Act of 1934, 47 U.S.C. § 152(a)–(b). Unsurprisingly given the construction that language had

been given in predecessor statutes, originally this allocation was understood to make the field of interstate

communications exclusively federal generally. See,

e.g., FRC v. Nelson Bros. Bond & Mortg. Co., 289 U.S.

266, 279 (1933) (“No state lines divide the radio waves,

and national regulation is not only appropriate but essential to the efficient use of radio facilities.”); Allen B.

Dumont Lab’ys v. Carroll, 184 F.2d 153, 156 (3d Cir.

1950) (“We think it is clear that Congress has occupied

fully the field of television regulation and that that

field is no longer open to the States.”); Ivy Broad. Co.

v. Am. Tel. & Tel. Co., 391 F.2d 486, 491 (2d Cir. 1968)

(“[T]he duties, charges and liabilities of telegraph or

telephone companies with respect to interstate communications service are to be governed solely by federal law and . . . the states are precluded from acting

in this area.”). As this Court later noted, the plain language of the Communications Act “divide[s] the

world . . . into two hemispheres—one comprised of interstate service, over which the FCC would have plenary authority, and the other made up of intrastate

service, over which the States would retain exclusive

jurisdiction,” even though actions regulators take

“within their respective domains” can affect “the other

‘hemisphere.’” La. Pub. Serv. Comm’n v. FCC, 476 U.S.

355, 360 (1986).

19

In other words, according to the original meaning

of Section 2 of the Communications Act of 1934, the

field of interstate communications is “inherently federal in character.” Buckman Co., 531 U.S. at 347.

Preemption is therefore innate—that is, “it may be

presumed,” Ouellette, 479 U.S. at 491—except insofar

as “congressional action” provides otherwise. Leisy,

135 U.S. at 108; cf. C & A Carbone, Inc. v. Town of

Clarkstown, 511 U.S. 383, 408 (1994) (O’Connor, J.,

concurring in the judgment) (“Congress must be ‘unmistakably clear’ before we will conclude that it intended to permit state regulation which would otherwise violate the dormant Commerce Clause.” (quoting

S.-Cent. Timber Dev., Inc. v. Wunnicke, 467 U.S. 82,

91 (1984))). In this field, too, a presumption against

preemption has no place.

II.

Applying

the

Presumption

Against

Preemption in Traditionally Federal

Fields Exacerbates the Very Problems

That the Constitution’s Structure Is

Meant to Ameliorate.

The commitment of historically national fields to

the federal government reflects the Framers’ conviction baked into the Constitution’s structure “that the

peoples of the several states must sink or swim together, and that in the long run prosperity and salvation are in union and not division.” Baldwin v. G.A.F.

Seelig, Inc., 294 U.S. 511, 523 (1935) (Cardozo, J.). As

James Madison explained, the commitment of interstate matters such as these to the national government “provide[s] for the harmony and proper intercourse among the States.” The Federalist No. 42

(James Madison); accord Pennsylvania v. West

20

Virginia, 262 U.S. 553, 596 (1923) (“By the Constitution . . . the power to regulate interstate commerce is

expressly committed to Congress and therefore impliedly forbidden to the states. . . . It means that in the

matter of interstate commerce we are a single nation—one and the same people.”). But too often in such

fields, the inapt presumption against preemption has

been wielded to frustrate these aims, undermine rather than reinforce the Constitution’s structure, and

create regulatory confusion.

Consider, for instance, the fundamental principle

that each State in the Union enjoys “equal dignity and

sovereignty,” Franchise Tax Bd. of Cal. v. Hyatt, 587

U.S. 230, 245 (2019), a principle “essential to the harmonious operation of the scheme upon which the Republic was organized,” Shelby County v. Holder, 570

U.S. 529, 544 (2013) (cleaned up). A necessary corollary of this principle is that no state “can enforce its

own policy” upon another. Kansas v. Colorado, 206

U.S. 46, 95 (1907). But when the presumption against

preemption is wrongly applied to regulations in traditionally federal fields, states can do just that.4

Under the principle of equal sovereignty, neither

states nor their subdivisions may “impose economic

sanctions on violators of its laws with the intent of

changing . . . lawful conduct in other States.” BMW of

4 But see Cummings v. Missouri, 71 U.S. (4 Wall.) 277, 325 (1866)

(“[W]hat cannot be done directly cannot be done indirectly. The

Constitution deals with substance, not shadows.”); cf. First

Choice Women’s Res. Ctrs., Inc. v. Davenport, 608 U.S. ----, 2026

WL 1153029, at *11 (2026) (“Our Constitution . . . prohibits subtle . . . interference with protected liberties no less than it does

heavy-handed frontal attacks.” (cleaned up)).

21

N. Am., Inc. v. Gore, 517 U.S. 559, 572 (1996). But absent the Court’s intervention, courts around the country are at risk of doing just that, by applying a presumption against preemption that would permit conflicting and overlapping state laws to govern in traditionally federal fields, contrary to congressional intent.

These problems are not merely theoretical: they

have arisen in recent years in cases implicating the

field of interstate communications impacting CTIA’s

members. For instance, in New York State Telecommunications Association, CTIA and several affiliated

trade associations challenged as preempted a New

York law that imposed rate regulations on the concededly interstate provision of broadband Internet service to certain New Yorkers. 101 F.4th at 139, 148,

148 n.10. Repeatedly invoking the presumption

against preemption, and ignoring the statutory background and original meaning of Section 2 of the Communications Act, the majority rejected this challenge,

reasoning that “nothing in the text suggests that the

FCC has exclusive jurisdiction over interstate communication.” Id. at 148–51. On this basis, New York’s law

regulating “the rates charged” for “interstate communications services” was upheld. Id. at 153. But as

Judge Sullivan—the author of the Second Circuit’s decision in Chevron Corp.—rightly noted in dissent, the

court’s decision wrongly “embolden[ed] states like

New York to impose costs on broadband internet service that extend well beyond their borders.” Id. at 169

(Sullivan, J., dissenting).

Or consider ACA Connects, another case in which

CTIA and affiliated trade associations sued to challenge as preempted a state law regulating the

22

inherently interstate activity of providing broadband

Internet service. 24 F.4th 1233. Not only ignoring the

original meaning of Section 2 of the Communications

Act but also interpreting the Act as if it “assum[ed]

that states . . . would have concurrent authority to regulate interstate services,” the court concluded that

CTIA and the other trade associations were “unlikely

to prevail on their argument” that the law was

preempted and affirmed the denial of a preliminary

injunction. Id. at 1248. And that had the predictable

effect of permitting California to “enforce its own policy” beyond its borders. Contra Kansas, 206 U.S. at 95;

see, e.g., Opening Br. of Pls.-Appellants Broadband

Provider Ass’ns at 61, ACA Connects, 24 F.4th 1233

(No. 21-15430), 2021 WL 1499801 (explaining how

mobile providers had been “forced to withdraw beneficial service offerings from the marketplace” generally because of the law).

But allowing one State to “effectively force other

States to regulate in accordance with [its] idiosyncratic state demands” does not comport with “the Constitution the Framers adopted in Philadelphia in

1787,” let alone the Communications Act. Nat’l Pork

Producers Council, 598 U.S. at 407 & n.3 (Kavanaugh,

J., concurring in part and dissenting in part) (defending the Pike balancing test’s role in effectuating this

constitutional commitment in cases involving nondiscriminatory state laws). And such a “chaotic regulatory structure,” Ouellette, 479 U.S. at 497, not only

contravenes the Framers’ design but also self-inflicts

economic harm on the Nation. See also Milwaukee III,

731 F.2d at 414 (“For a number of different states to

have independent and plenary regulatory authority

over a single discharge would lead to chaotic

23

confrontation between sovereign states.”); Pet. App.

45a (Samour, J., dissenting) (“Such local regulation

will invite chaos.”). Neither the Constitution, nor the

presumption against preemption meant to implement

its structure, compels such a result. Rather, in traditionally federal fields like the one at issue in this

case—or the one CTIA’s members operate in—the presumption against preemption has no place. To the contrary, preemption “may be presumed.” Ouellette, 479

U.S. at 491. The Court should use this opportunity to

make that point clear.

CONCLUSION

The Court should reverse the judgment of the Colorado Supreme Court.

Respectfully Submitted,

Thomas M. Johnson, Jr.

Counsel of Record

Joel S. Nolette

Brandon Beck

WILEY REIN LLP

2050 M Street NW

Washington, DC 20036

(202) 719-7000

tmjohnson@wiley.law

May 21, 2026

Counsel for Amicus Curiae