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 PROFESSOR WILLIAM W. BUZBEE

AS AMICUS CURIAE

IN SUPPORT OF RESPONDENTS

KIRTI DATLA

Counsel of Record

EARTHJUSTICE

1250 Eye Street NW

Floor 4

Washington, DC 20005

(202) 667-4500

kdatla@earthjustice.org

Counsel for Amicus Curiae

TABLE OF CONTENTS

Page(s)

TABLE OF AUTHORITIES………………………………….ii

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

INTRODUCTION AND

SUMMARY OF ARGUMENT .....................................2

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

I. This Court Should Decline Petitioners’

Request That It Create A Bespoke Clear

Statement Rule To Resolve This Case. ............5

II. Ordinary Preemption Principles Govern

The Statutory Question Here. ........................ 13

CONCLUSION .......................................................... 19

(i)

ii

TABLE OF AUTHORITIES

Page(s)

Cases

Biden v. Nebraska,

600 U.S. 477 (2023) ........................................... 9, 10

Bowe v. United States,

607 U.S. 13 (2026) ......................................... 2, 5, 13

Goodyear Atomic Corp. v. Miller,

486 U.S. 174 (1988) .................................................8

Gregory v. Ashcroft,

501 U.S. 452 (1991) .................................................7

Hencely v. Fluor Corp.,

608 U.S. 31 (2026) ....................................... 3, 14, 15

Int’l Paper Co. v. Ouellette,

479 U.S. 481 (1987) .................................................6

Learning Res., Inc. v. Trump,

607 U.S. 229 (2026) ........................................... 2, 10

Loper Bright Enters. v. Raimondo,

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

Nat’l Pork Producers Council v. Ross,

598 U.S. 356 (2023) ............................................... 17

Sackett v. EPA,

598 U.S. 651 (2023) ............................................... 16

United States v. Standard Oil Co. of Cal.,

332 U.S. 301 (1947) ............................................... 14

iii

TABLE OF AUTHORITIES—Continued

Page(s)

U.S. Forest Serv. v. Cowpasture River Pres. Ass’n,

590 U.S. 604 (2020) .................................................7

Williams v. Lee,

358 U.S. 217 (1959) .................................................9

Statutes

33 U.S.C. § 1251(b) .................................................... 16

42 U.S.C. § 7401(a)(3) ............................................... 15

42 U.S.C. § 7401(c) ................................................ 4, 16

42 U.S.C. § 7416 .............................................. 4, 17, 18

42 U.S.C. § 7573 ........................................................ 17

42 U.S.C. § 7604(e) ................................................ 4, 17

Other Authorities

Amy Coney Barrett, Substantive Canons and

Faithful Agency,

90 B.U. L. Rev. 109 (2010) ......................................2

William W. Buzbee, Asymmetrical Regulation: Risk,

Preemption, & the Floor/Ceiling Distinction,

82 N.Y.U. L. Rev. 1547 (2007) ........................ 16, 18

Benjamin Eidelson & Matthew C. Stephenson, The

Incompatibility of Substantive Canons and

Textualism,

137 Harv. L. Rev. 515 (2023) ................................ 10

iv

TABLE OF AUTHORITIES—Continued

Page(s)

Kirsten H. Engel, Harnessing the Benefits of

Dynamic Federalism in Environmental Law,

56 Emory L.J. 159 (2006) ...................................... 11

William N. Eskridge, Jr., et al., Textualism’s

Defining Moment,

123 Colum. L. Rev. 1611 (2023)............................ 12

Heather K. Gerken, Federalism 3.0,

105 Cal. L. Rev. 1695 (2017) ................................. 16

Anita S. Krishnakumar, Reconsidering Substantive

Canons,

84 U. Chi. L. Rev. 825 (2017)................................ 11

John F. Manning, Clear Statement Rules and the

Constitution,

110 Colum. L. Rev. 399 (2010)........................ 10, 11

Nina A. Mendelson, Change, Creation, and

Unpredictability in Statutory Interpretation:

Interpretive Canon Use in the Roberts Court’s First

Decade,

117 Mich. L. Rev. 71 (2018) .................................. 13

Antonin Scalia, A Matter of Interpretation

(1997) .....................................................................13

INTEREST OF AMICUS CURIAE

William W. Buzbee holds the inaugural Edward

and Carole Walter Professor chair and is a Professor

of Law at Georgetown University Law Center and the

Faculty Director of the Georgetown Climate Center. 1

Professor Buzbee’s work has extensively addressed

the application of preemption and statutory interpretation principles to federal environmental statutes.

See, e.g., Preemption Choice: The Theory, Law, and

Reality of Federalism’s Core Question (William W.

Buzbee ed., 2008); William W. Buzbee, FederalismFacilitated Regulatory Innovation and Regression in a

Time of Environmental Legislative Gridlock, 28 Geo.

Env’t L. Rev. 451 (2016). He believes that legal scholarship should be concerned with, and made useful to,

courts’ resolution of these issues. To that end, he has

drawn on that work in amicus briefs in prior cases

that implicated these issues. See, e.g., Br. of Preemption Scholars, Montgomery v. Caribe Transport II,

LLC, 146 S. Ct. 1199 (2026) (No. 24-1238); Br. of Admin. & Fed. Regul. L. Professors, Loper Bright Enters.

v. Raimondo, 603 U.S. 369 (2024) (No. 22-451); Br. of

Pub. L. Scholars, Merck Sharp & Dohme Corp. v. Albrecht, 587 U.S. 299 (2019) (No. 17-290).

Professor Buzbee submits this amicus brief solely

in his individual capacity as a lawyer and scholar, and

the views expressed in this amicus brief should not be

attributed to his institution.

1 No counsel for a party authored this brief in whole or in

part, and no such counsel, party, or other person or entity—other

than amicus curiae and his counsel—made a monetary contribution intended to fund the preparation or submission of this brief.

(1)

2

INTRODUCTION AND

SUMMARY OF ARGUMENT

“Courts interpret statutes, no matter the context,

based on the traditional tools of statutory construction, not individual policy preferences.” Loper Bright

Enters. v. Raimondo, 603 U.S. 369, 403 (2024). Petitioners ask this Court to depart from those traditional

rules of statutory interpretation in two different ways

here: by creating a bespoke clear-statement rule and

by applying a presumption of preemption. Both would

burden Congress with an obligation to speak clearly

on an issue, to a court’s satisfaction, before its laws

will be read to preserve state authority to touch on

that issue. And both are so malleable as to risk allowing judicial preferences to substitute for the political

branches’ actual choices.

Petitioners’ proposed good-for-this-case rules “may

suit [their] present needs,” but each “lacks any

grounding in law,” Bowe v. United States, 607 U.S. 13,

57–58 (2026) (Gorsuch, J., dissenting). This Court

should reject both.

As to the proposed new clear-statement rule, it is

exactly the kind of vague, values-enforcing substantive canon that members of this Court have pointed to

when expressing “skeptic[ism] about adding new ones

to the mix.” Learning Res., Inc. v. Trump, 607 U.S.

229, 303 (2026) (Barrett, J., concurring). When asking

this Court to invent a new substantive canon, a party

must—at a minimum—explain why the canon’s purported value outweighs its costs. Cf. Amy Coney Barrett, Substantive Canons and Faithful Agency, 90 B.U.

L. Rev. 109, 181 (2010) (“The point is simply to say

that such an inquiry must be undertaken.”).

3

Petitioners’ three-sentence treatment of their proposed clear-statement rule (at 30–31) does not contain

that explanation. This Court can reject it for that reason alone. But even taken on its own terms, the proposed rule is indefensible.

All clear-statement rules impose a clarity tax on

Congress, but petitioners’ proposed rule would levy a

particularly severe one. It is deeply unclear when, exactly, petitioners’ rule would be triggered, as they refer only (at 30) to when a statute upsets some unspecified balance of power between the federal and state

governments. And it is equally unclear what statutory text, exactly, could overcome their rule once triggered. Adopting petitioners’ proposed rule would hold

the Clean Air Act’s drafters to a standard that they

could not have known of, would provide future drafters with no guidance about how to navigate the rule,

and would put future courts at risk of navigating the

rule’s fuzziness based on policy preferences.

As to petitioners’ proposal to presume preemption,

it is an attempt to reach the same place dressed up in

different, but equally doctrinally lacking, garb. Petitioners rely on cases addressing the few areas that implicate uniquely federal interests, but those cases do

not presume preemption. Instead, in those few areas,

state law is preempted only if there is “a significant

conflict between an identifiable federal policy or interest and the operation of state law.” Hencely v. Fluor

Corp., 608 U.S. 31, 39 (2026) (quotation and brackets

omitted). Regardless, the Clean Air Act does not address uniquely federal interests within the meaning of

the cases petitioners invoke. The Act’s very first provision “encourag[es] . . . reasonable Federal, State,

4

and local governmental actions, consistent with the

[Act], for pollution prevention” as “[a] primary goal.”

42 U.S.C. § 7401(c). It contains multiple savings

clauses that make clear that federal standards operate as a floor, not a ceiling. See id. §§ 7416, 7604(e).

And where the Act does limit state and local authority, it does so expressly. The Clean Air Act thus welcomes state and local government efforts to address

air pollution.

It would disrespect the political branches to presume preemption here. As a general matter, very few

federal statutes expressly push traditional state police powers out of the picture. Presuming that a given

statute implicitly does so therefore risks undermining

legislative supremacy by assuming that Congress has

taken a step that it almost never does. Given the

Clean Air Act’s invitation to state and local governments, presuming that it implicitly precludes traditional state tort claims is especially unwarranted.

There is much else wrong with petitioners’ arguments, but this brief focuses on these two statutory

interpretation issues because of the consequences of

getting them wrong. Parties often ask courts to create

bespoke interpretive rules to tilt a case in their favor,

especially if they are concerned that the ordinary

rules do not favor them. But statutory interpretation

rules apply across the U.S. Code, and so a rule issued

in one case will almost inevitably escape containment

and be invoked across other cases, and other statutes.

Petitioners’ desire to win their case does not justify

new rules that will create problems for Congress and

the courts going forward.

This Court should affirm.

5

ARGUMENT

I. This Court Should Decline Petitioners’

Request That It Create A Bespoke Clear

Statement Rule To Resolve This Case.

Petitioners claim that respondents’ suit implicates

a set of issues that are “distinctively federal in character” and that Congress must have “clearly express[ed] its intention to” authorize state tort law to

address those issues before respondents’ suit can proceed. Petrs’ Br. at 30 (quotation omitted). In doing so,

petitioners ask this Court to fashion a new clear-statement rule to resolve this case. As members of this

Court and scholars of its jurisprudence alike have recognized, rules of this kind often stand on shaky footing. Petitioners do not attempt to explain why their

proposed new rule would avoid the doctrinal problems

associated with clear-statement rules. 2 It would not.

This Court should not accept the invitation to adopt

their rule.

1. Petitioners are asking this Court to “conjur[e] up

a clear-statement rule to support their course.” Bowe,

607 U.S. at 57 (Gorsuch, J., dissenting). They claim

that when a question arises over whether a federal

statute allows a state tort suit that allegedly implicates a “dispute[] over the regulation of air and water

in their ambient or interstate aspects,” Petrs’ Br. at

13, the federal statute must expressly authorize state

tort suits of this kind, or else the suit cannot proceed.

If a clear-statement applied in this context, then this

2 As respondents note, the United States does not join in pe-

titioners’ request. Resps’ Br. 29–30.

6

Court would have applied it in cases that implicate

that question. But it has not.

Instead, this Court has applied ordinary statutory

interpretation principles to look for affirmative evidence of preemption. In International Paper Co. v.

Ouellette, the question was “whether the [Clean Water] Act pre-empts Vermont common law to the extent

that law may impose liability on a New York point

source.” 479 U.S. 481, 491 (1987). In laying out the

framework for deciding the question, this Court noted

that “courts should not lightly infer pre-emption” but

might still find it under circumstances evidencing

field, conflict, or obstacle preemption. Id. at 491–492.

Ouellette applied that familiar framework even after it specifically recognized that the Clean Water Act

did “not speak directly to the” question before the

Court. Id. at 493. That is, the Act did not “clearly

express its intention to,” Petrs’ Br. at 30, authorize the

Vermonters’ suit at issue. If a clear-statement rule

applied (as petitioners contend), that would have

ended the matter in Ouellette. But this Court went on

to “examin[e] the [Act] as a whole, its purposes and its

history.” Ouellette, 479 U.S. at 493. Only then did it

conclude that the Act “precludes a court from applying

the law of an affected State against an out-of-state

source. Id. at 494. Instead, the law of the pollution

source’s state applied to the claims for interstate pollution harms. See id. at 497 (“[N]othing in the Act

bars aggrieved individuals from bringing a nuisance

claim pursuant to the law of the source State.”).

Tellingly, petitioners do not identify any case in

which this Court has mentioned, or applied, their proposed clear-statement rule in this context. Instead,

7

they point (at 30–31) to a series of disconnected cases

that addressed distinct contexts. These cases provide

no support for their proposed new rule.

Petitioners’ first case, to the extent that it establishes a clear-statement rule, did so based on concerns

about a federal statute’s potential reduction of state

land-use authority. There, the question was whether

the U.S. Forest Service “has authority under the Mineral Leasing Act to grant rights-of-way through lands

within national forests traversed by the Appalachian

Trail.” U.S. Forest Serv. v. Cowpasture River Pres.

Ass’n, 590 U.S. 604, 607–608 (2020) (citation omitted).

In answering yes, this Court examined another statute, the National Trails System Act, to determine

whether it transferred jurisdiction of the lands in

question to another agency and concluded that it had

not. See id. at 613–619. It described the contrary interpretation as “ha[ving] striking implications for federalism and private property rights,” expressing concern about the policy consequences of giving the National Park Service some degree of control over private, state, and local lands that fall within the National Park System. Id. at 621. That concern about

diminishment of state authority led this Court to state

that its “precedents require Congress to enact exceedingly clear language if it wishes to significantly alter

the balance between federal and state power and the

power of the Government over private property.” Id.

at 621–622. 3 Petitioners’ proposed rule would, in

3 For this proposition, this Court did not direct the reader to

multiple “precedents.” Cowpasture River Pres. Ass’n, 590 U.S. at

621. It offered only a cf. citation to Gregory v. Ashcroft, 501 U.S.

452, 460 (1991). See Cowpasture River Pres. Ass’n, 590 U.S. at

8

contrast, diminish traditional state police powers.

Petitioners’ second case did not require this Court

to resolve whether a clear-statement rule applied to

the statute before it, nor did the case address environmental harms. The question was whether a state

workers’ compensation law “that provide[d] an increased award for injuries resulting from an employer’s violation of a state safety regulation” applied

to “a private contractor operating a federally owned

nuclear production facility.” Goodyear Atomic Corp.

v. Miller, 486 U.S. 174, 176 (1988). This Court stated

that the Supremacy Clause shields “activities of federal installations . . . from direct state regulation unless Congress provides clear and unambiguous authorization.” Id. at 180 (internal quotation marks

omitted). But the state law at issue did not involve

“direct state regulation”; it involved a supplemental

workers’ compensation award. Id. at 181–182. The

Court did not need to decide whether—despite that

difference—the Supremacy Clause barred that award

absent authorization because a federal statute did authorize it. See id. at 182.

And petitioners’ third case is similarly far afield,

as it addressed the displacement of tribal jurisdiction.

There, the question was whether a state court could

“exercise jurisdiction over civil suits by non-Indians

622. That case, in turn, referred to “an acknowledgment that the

States retain substantial sovereign powers under our constitutional scheme, powers with which Congress does not readily interfere.” Ashcroft, 501 U.S. at 461. Ashcroft, then, like Cowpasture River Preservation Association, was concerned with federal

statutes’ ability to diminish traditional state authorities. See

Resps’ Br. at 45 n.18.

9

against Indians though the action arises on an Indian

reservation.” Williams v. Lee, 358 U.S. 217, 218

(1959). In answering no, this Court explained that

“tribal jurisdiction or that expressly conferred on

other courts by Congress has remained exclusive.” Id.

at 220. No federal statute gave the state court jurisdiction over the controversy at issue. See id. at 222.

In sum, petitioners are proposing a new, bespoke

clear-statement rule for this case. As discussed next,

this Court should reject their proposal.

2. Petitioners’ proposed clear-statement rule falls

within the category of substantive canons: “rules of

construction that advance values external to a statute.” Biden v. Nebraska, 600 U.S. 477, 508 (2023)

(Barrett, J., concurring). 4 Petitioners do not clarify

what value, exactly, their proposed rule advances.

But it appears to be an unquantified view about the

appropriate balance of power between the federal and

state governments. See Petrs’ Br. at 30.

Petitioners do not claim that their proposed rule is

necessary to avoid a constitutional problem, but even

if they did, that justification would not suffice. As respondents note, see Resps’ Br. at 29–30, their state

tort suit is either constitutionally permissible or it is

not. If not, the Act’s clarity is irrelevant. Petitioners’

proposed rule thus does work—that is, determines the

4 These “stand in contrast to linguistic or descriptive canons,

which are designed to reflect grammatical rules . . . or speech

patterns.” Nebraska, 600 U.S. at 508 n.1 (Barrett, J., concurring). Petitioners do not (at 30–31) defend their proposed clearstatement rule as a linguistic canon (that is, one based in an understanding of how specific statutory language is ordinarily used

and understood).

10

viability of respondents’ suit—only if the suit is constitutionally permissible but the Act’s text does not allow it with some unspecified required level of clarity.

In that circumstance, “it is difficult to see how nullifying that [suit]—based on . . ., a federalism canon, or

the like—could possibly be justified as a means of

averting a constitutional violation that does not exist.”

Benjamin Eidelson & Matthew C. Stephenson, The Incompatibility of Substantive Canons and Textualism,

137 Harv. L. Rev. 515, 561 (2023); see also Learning

Res., Inc., 607 U.S. at 302 (Barrett, J., concurring)

(“But if the Constitution permits Congress to give . . .

a particular power, who are we to get in the way?”).

The shaky case for vague, values-enforcing clearstatement rules like the one that petitioners propose

here have generated “skeptic[ism] about adding new

ones to the mix. Learning Res., 607 U.S. at 303 (Barrett, J., concurring). That skepticism is more than

warranted here. Petitioners’ proposed rule bears all

the hallmarks of the kind of rule that members of this

Court and a robust academic literature have explained are least justifiable.

Petitioners’ proposed rule will “impose a clarity tax

on the legislative process” in service of “personal preferences about which commitments to emphasize.”

John F. Manning, Clear Statement Rules and the Constitution, 110 Colum. L. Rev. 399, 426 (2010). “[B]y

demanding that [the legislature] speak unequivocally

if it wants to accomplish certain ends,” it intrudes on

the province and duty of that branch to enact policy

decisions into law. Nebraska, 600 U.S. at 508 (Barrett, J., concurring). This risk is especially high

when—as here—a new rule is floated that would

11

apply to an existing statute. In that circumstance, the

statute’s enactors had no notice that judicially created

heightened clear statement demands might apply to

the bill before them. See Anita S. Krishnakumar, Reconsidering Substantive Canons, 84 U. Chi. L. Rev.

825, 883 (2017) (The problem “is particularly disturbing when” a new rule is applied “to an older statute,

enacted . . . when different statutory interpretation

techniques predominated . . . .”).

Petitioners’ proposed rule imposes an especially

high clarity tax because its trigger is indeterminate.

At some level, all federal antipollution and natural resource-protecting laws overlap with state and local

governmental authority to address land use, conservation, public health, and safety risks. See, e.g.,

Kirsten H. Engel, Harnessing the Benefits of Dynamic

Federalism in Environmental Law, 56 Emory L.J.

159, 166 (2006) (explaining that “jurisdictional overlap is the norm, not the exception”). When the political branches act, what balance that they strike within

this jurisdictional overlap will “significantly alter[]

the balance between federal and state power” and

trigger petitioners’ proposed rule? Petrs’ Br. at 30

(quotation omitted). Who can say? (And petitioners

do not say.) Petitioners’ proposed rule provides no

guidance to future legislative drafters about how clear

they will need to be to accomplish their policy goals.

See Manning, supra, at 434 (Rules triggered by “statutes that (in [a court’s] view) disrupt federalism” address “a structural value . . . abstracted to an unhelpful level of generality.”).

Petitioners’ proposed rule would impose a tax on

the judiciary as well.

Once mentioned, clear-

12

statement rules of this kind must be addressed in future cases. This often requires judges to answer questions that the creating court may have left unanswered. Is the rule a clear-statement rule after all? 5

Has it been triggered? 6 See William N. Eskridge, Jr.,

et al., Textualism’s Defining Moment, 123 Colum. L.

Rev. 1611, 1683 (2023) (“Should the judge apply the

canon? . . . Should there be an exception to the

canon?”). And if it is triggered, “[h]ow specific does

that statutory language have to be?” 7 Id.; see also id.

(“Once launched,” these canons typically evolve “from

presumptions to clear statement rules to super-strong

clear statement rules.”).

5 See, e.g., Tr. of Oral Arg. at 15, FS Credit Opportunities

Corp. v. Saba Capital Master Fund, Ltd., 146 S. Ct. 1546 (2026)

(No. 24-345) (Barrett, J.) (“I don’t read Sandoval to necessarily

require or to require a clear statement.”).

6 See, e.g., Tr. of Oral Arg. at 63–64, Hencely v. Flour Corp.,

608 U.S. 31 (2026) (No. 24-924) (Thomas, J.) (“[H]ow would you

define uniquely federal interests? . . . I mean, you could argue

that the interstate highway system is uniquely federal. I just –

I don’t understand how we are going to limit that.”).

7 See, e.g., Tr. of Oral Arg. at 10, Riley v. Bondi, 606 U.S. 259

(2025) (No. 23-1270) (Roberts, C.J.) (“I mean, is it really a magic

words case, that the statute has to say ‘and this is jurisdictional’?”); Tr. of Oral Arg. at 25, Boechler, P.C., v. Comm’r of Internal Revenue, 596 U.S. 199 (2022) (No. 20-1472) (Kagan, J.)

(“[W]e’ve always said that there are no magic words. So how do

we draw that line? . . . [H]ow can we insist that there are no

magic words and yet insist that there be conditional language of

some kind?”); Tr. of Oral Arg. at 48, Dep’t of Ag. Rural Dev. Rural

Housing Serv. v. Kirtz, 601 U.S. 42 (No. 22-846) (Jackson, J.)

(“[I]s the government not conceding that we have said that you

can satisfy the clear statement rule by implication? . . . [S]o an

implication could occur when what?”).

13

Perhaps future courts might find ways to avoid answering these difficult questions. See Nina A. Mendelson, Change, Creation, and Unpredictability in

Statutory Interpretation: Interpretive Canon Use in

the Roberts Court’s First Decade, 117 Mich. L. Rev. 71,

135 (2018) (conducting an empirical study to describe

a pattern of “devising new interpretive canons, abandoning old ones, and deciding whether to deploy them

based on reasons that appear difficult to pin down”).

But that would only compound the problems that

these clear-statement rules pose. “Unpredictable

canon use, blurry canon contours, or a general atmosphere of changeability” undermine arguments that

these rules provide a predictable “interpretive background” and likely reduce “drafters’ incentives to

maintain overall awareness of canon use.” Id. at 88.

Clear-statement rules like the one that petitioners

propose here impose “a lot of trouble,” Antonin Scalia,

A Matter of Interpretation 28 (1997). Their “rule may

suit [petitioners’] present needs,” but it “lacks any

grounding in law,” Bowe, 607 U.S. at 57–58 (Gorsuch,

J., dissenting). This Court should reject it.

II. Ordinary Preemption Principles Govern

The Statutory Question Here.

Petitioners offer another route to the same problematic destination when they urge this Court (at 30,

44) to say that respondents’ state-law suit implicates

uniquely federal interests and is therefore preempted

absent statutory authorization. Again, this Court has

not followed that route when addressing this context

before in Ouellette; it did the opposite. See supra at 6

(discussing the inclusion of the presumption against

preemption in the framework for analyzing

14

preemption). And because this argument lands in the

same place as petitioners’ proposed clear-statement

rule—flipping the default of non-preemption and imposing a burden on Congress to act affirmatively—the

objections to that rule apply equally here.

There are more reasons to reject petitioners’ presumption-of-preemption argument. To start, they far

overread the “uniquely federal interest” line of cases

that they try and fit this case into, ignoring guidance

that this Court provided just a few months ago. In

any event, the Clean Air Act’s text and structure make

clear both that it does not implicate that line of cases

and that it is incompatible with a presumption of

preemption. “[O]rdinary statutory preemption analysis applies.” Resps’ Br. at 45.

1. Petitioners argue that “there is no need for” Congress to act affirmatively “to foreclose the application

of state law” if a case implicates an “issue [that] is ‘distinctively federal in character.’ ” Petrs’ Br. at 30 (quoting United States v. Standard Oil Co. of Cal., 332 U.S.

301, 305 (1947)). Even if this case did implicate some

uniquely federal interest (more on that later), that is

not how preemption would work.

Even in “rare areas of uniquely federal interest,”

“the identification of a uniquely federal interest does

not . . . end the inquiry” into preemption. Hencely, 608

U.S. at 39–40 (quotation omitted). Instead, state law

is preempted only if there is “a significant conflict . . .

between an identifiable federal policy or interest and

the operation of state law.” Id. at 39 (quotation and

brackets omitted). 8 Hencely just made quite clear that

8 This is a “narrow[]” doctrine, one that “will rarely apply

15

petitioners’ view (at 44)—that a mere inconsistency or

dull conflict will result in preemption in the rare areas

of uniquely federal interests—is not the law.

What is more, Hencely rejected an attempt—the

same play that petitioners run here—to expand the

uniquely federal interest line of cases. There, “[w]ithout any constitutional or statutory text expressly supporting preemption,” a party asserted that “all claims

against contractors engaged in combatant activities

under the military’s command” are preempted because they implicate uniquely federal interests.

Hencely, 608 U.S. at 38. But this Court described

prior precedent as limiting preemption to the “special

circumstance in which the contractor has a defense

because the government has directed a contractor to

do the very thing that is the subject of the claim.” Id.

at 41 (quotation omitted). In rejecting broader

preemption, this Court explained that its conclusion

“should come as no surprise” because “Congress

knows full well how to make its intention to preclude

private liability known.” Id. at 42 (quotation omitted).

2. The text and structure of the Clean Air Act also

make clear that it does not implicate uniquely federal

interests and that there is no basis to assume a significant conflict between state tort suits and the Act.

The Clean Air Act’s text and structure preclude a

conclusion that the Act addresses uniquely federal interests. After all, the Act states “that air pollution

prevention . . . and control at its source is the primary

responsibility of States and local governments.” 42

when litigation is purely between private parties.” Hencely, 608

U.S. at 39 (quotation omitted).

16

U.S.C. § 7401(a)(3); see also Sackett v. EPA, 598 U.S.

651, 680 (2023) (reading 33 U.S.C. § 1251(b), a parallel provision of the Clean Water Act, to counsel

against narrowing state authority). The Act also “encourag[es] . . . reasonable Federal, State, and local

governmental actions, consistent with the [Act’s provisions], for pollution prevention” as “[a] primary

goal.” 42 U.S.C. § 7401(c). And the Act, like other environmental statutes that address harm from interstate pollution, assigns “roles to federal regulators,

but also seek[s] to entice state and local regulators to

join in the pursuit of federally identified ends.” William W. Buzbee, Asymmetrical Regulation: Risk,

Preemption, & the Floor/Ceiling Distinction, 82

N.Y.U. L. Rev. 1547, 1564–1565 (2007). The enactors

of this text would not have viewed the Act as implicating a uniquely federal interest as the cases petitioners

invoke use that phrase. 9

And those enactors would not have thought that

any use of state law that relates in some way to air

pollution would be preempted unless the Act specifically authorized it. Such federal boxing out of state

authority is the exception, not the norm. “[F]ew statutes explicitly preempt state common law actions.”

Id. at 1591; see also id. at 1561 n.36 (providing

9 It is difficult to see what would not implicate a uniquely

federal interest if the Clean Air Act does. See Resps’ Br. at 40–

41 (criticizing the haziness of this phrase); see also Heather K.

Gerken, Federalism 3.0, 105 Cal. L. Rev. 1695, 1699–1700 (2017)

(explaining that “neither the state nor the federal government

presides over its own empire” but instead “[o]verlap and interdependence are the rule” and offering environmental law, health

care, telecommunications, and financial regulation as examples).

17

examples). Most “say nothing precluding common law

liabilities.” Id. at 1591. As a result, arguments that

any given statute precludes any additional state and

local protections when its text does not expressly do so

raise “a serious question about fealty to legislative supremacy.” Id. “[T]he Framers equipped Congress

with considerable power to . . . preempt contrary state

laws,” and “extreme caution is warranted before a

court deploys . . . implied authority” to infer preemption that Congress has not written into law. Nat’l

Pork Producers Council v. Ross, 598 U.S. 356, 390

(2023) (quotation omitted).

The Clean Air Act cannot be read to contain some

implicit preference for boxing out state and local law;

instead, its text invites the use of state and local law

to address air pollution. See supra at 15–16 (discussing provisions that describe air pollution control as a

joint federal, state, and local project). Indeed, the Act

takes care not to “preclude or deny the right of any

State or political subdivision thereof” to adopt its own

emissions standards, limitations, or controls, except

that they may not adopt any that are “less stringent”

than a relevant federal standard under the Act. 42

U.S.C. § 7416. And the Act makes plain that it does

not “restrict any right which any person (or class of

persons) may have under any statute or common law

to seek enforcement of any emission standard or limitation or to seek any other relief.” Id. § 7604(e) (emphasis added). The Act preempts state and local powers in only a few circumstances, and where it does, it

does so with clear, express language. See, e.g., id.

§ 7573 (“No State or political subdivision thereof may

adopt or attempt to enforce any standard respecting

emissions of any air pollutant from any aircraft or

18

engine thereof unless such standard is identical to a

standard applicable to such aircraft under this part.”);

see also id. § 7416 (exempting cross-referenced express preemption provisions).

Given this, Petitioners’ claim (at 33–34) that the

Act’s savings clauses are evidence that the Act kills off

any room for state law that the clauses do not expressly preserve is wrong. These kinds of savings

clauses simply make clear that the Clean Air Act sets

a regulatory floor, rather than a ceiling that prohibits

state and local law from going further. Buzbee, supra,

at 1554 (“Federal floors preclude less stringent state

and local regulation, but allow for additional and more

stringent regulation and typically are accompanied by

savings clauses and cooperative regulatory structures.”). They do not close the door to all other state

and local law that may touch on air pollution, especially given the express invitation to the use of state

and local law in the rest of the Act. See Resps’ Br. at

48–49 (discussing Ouellette’s rejection of field preemption in the Clean Water Act for similar reasons).

Again, “Congress undoubtedly knows how to effect

a strongly or completely preemptive regime, much as

it knows how to retain significant state, local, and

common law roles . . . .” Buzbee, supra, at 1613. The

Act’s text and context show that Congress did the latter when it comes to air pollution, welcoming and preserving state and local authority. This Court should

respect this congressional judgment, which reflects

longstanding federalism norms, and reject petitioners’

presumption of preemption.

19

CONCLUSION

The Court should affirm.

Respectfully submitted,

KIRTI DATLA

Counsel of Record

EARTHJUSTICE

1250 Eye Street NW

Floor 4

Washington, DC 20005

(202) 667-4500

kdatla@earthjustice.org

Counsel for Amicus Curiae

August 3, 2026