Petition for Writ of Certiorari — Kentucky, et al., Petitioners v. Environmental Protection Agency, et al.

No. 26-___

In the Supreme Court of the United States

COMMONWEALTH OF KENTUCKY,

STATE OF WEST VIRGINIA, ET AL.

Petitioners,

v.

U.S. ENVIRONMENTAL PROTECTION AGENCY, ET AL.

Respondents.

On Petition for Writ of Certiorari

to the United States Court of Appeals

for the District of Columbia Circuit

PETITION FOR WRIT OF CERTIORARI

RUSSELL COLEMAN

Attorney General

Office of the Kentucky

Attorney General

1024 Capital Center

Drive, Suite 200

Frankfort, KY 40601

(502) 696-5300

Matt.Kuhn@ky.gov

MATTHEW F. KUHN

Solicitor General

Counsel of Record

JOHN H. HEYBURN

Principal Deputy

Solicitor General

JACOB M. ABRAHAMSON

Deputy Solicitor General

(Additional Counsel Below)

Office of the

West Virginia

Attorney General

State Capitol Complex

Building 1, Room E-26

Charleston, West

Virginia 25305

(304) 558-2021

mwilliams@wvago.gov

JOHN B. MCCUSKEY

Attorney General

MICHAEL R. WILLIAMS

Solicitor General

(Additional Counsel Listed After Signature Block)

i

QUESTIONS PRESENTED

The Clean Air Act allows the Environmental Protection Agency (EPA) to revise a national ambient air

quality standard (NAAQS) only after a “thorough review” of its air-quality criteria and the current standard. 42 U.S.C. § 7409(d)(1). But in 2024, EPA used a

short-circuited reconsideration process—involving an

intentionally narrow review of a few limited studies—

to revise the air-quality standards for fine particulate

matter (PM2.5) to the most restrictive level ever. Although EPA later disavowed any power to revise

NAAQS without a thorough review, the D.C. Circuit

rejected that concession and approved an expansive

view of EPA’s authority anyway.

The questions presented are:

1. Whether the Clean Air Act gives EPA the authority

to revise NAAQS without conducting a thorough

review merely because the revision occurs before

the normal, five-year review.

2. Whether the Clean Air Act bars EPA from considering the costs and feasibility of revising NAAQS

when deciding whether to exercise its discretion to

undertake a revision before the normal, five-year

review.

ii

PARTIES TO THE PROCEEDING

The petitioners are the Commonwealth of Kentucky, the State of West Virginia, the State of Alabama, the State of Alaska, the State of Arkansas, the

State of Florida, the State of Georgia, the State of

Idaho, the State of Indiana, the State of Iowa, the

State of Kansas, the State of Louisiana, the State of

Mississippi, the State of Missouri, the State of Montana, the State of Nebraska, the State of North Dakota, the State of Ohio, the State of Oklahoma, the

State of South Carolina, the State of South Dakota,

the State of Tennessee, the State of Utah, the State of

Wyoming, the State of Texas, and the Texas Commission on Environmental Quality.

The respondents are the U.S. Environmental Protection Agency and Lee M. Zeldin, in his official capacity as Administrator of the U.S. Environmental Protection Agency.

Additional petitioners in the court of appeals were

the Chamber of Commerce of the United States of

America, the American Chemistry Council, the American Forest & Paper Association, the American Petroleum Institute, the American Wood Council, the National Association of Manufacturers, the National

Mining Association, the American Cement Association, the President of the Arizona State Senate Warren Peterson, Speaker of the Arizona House of Representatives Ben Toma, the Arizona Chamber of Commerce and Industry, and the Essential Minerals Association.

Intervenors in support of respondents in the court

of appeals were the Alliance of Nurses for Healthy Environments, the American Lung Association, Citizens

iii

for Pennsylvania’s Future, the Conservation Law

Foundation, the Environmental Defense Fund, the

Natural Resources Defense Council, the Northeast

Ohio Community Resilience Centre, the Rio Grande

International Study Center, the Sierra Club, the State

of California, the State of Arizona, the State of Connecticut, the State of Illinois, the State of Maryland,

the State of Michigan, the State of Minnesota, the

State of New Jersey, the State of New York, the State

of Oregon, the State of Rhode Island, the State of Vermont, the State of Washington, the State of Wisconsin,

the Commonwealth of Massachusetts, the Commonwealth of Pennsylvania, the District of Columbia, the

City of New York, and Harris County, Texas.

iv

STATEMENT OF RELATED PROCEEDINGS

1. This case began as petitions for review consolidated in the D.C. Circuit. That case is Kentucky, et

al. v. EPA, et al., Nos. 24-1050, 24-1051, 24-1052,

24-1073, 24-1091 (D.C. Cir. June 26, 2026).

v

TABLE OF CONTENTS

Page

QUESTIONS PRESENTED ........................................ i

PARTIES TO THE PROCEEDING ............................ii

STATEMENT OF RELATED PROCEEDINGS ........ iv

TABLE OF AUTHORITIES ...................................... vii

INTRODUCTION ........................................................ 1

OPINIONS BELOW .................................................... 3

JURISDICTION .......................................................... 3

STATUTORY PROVISIONS INVOLVED .................. 4

STATEMENT OF THE CASE .................................... 4

I. EPA sets air-quality standards, and States

implement them. .................................................... 4

II. In 2024, EPA decided to revise the NAAQS for PM

ahead of schedule and without a thorough review.

................................................................................ 8

III. Petitioners challenged the 2024 Rule in the D.C.

Circuit. .................................................................. 11

REASONS TO GRANT THE PETITION ................. 13

I. This case presents questions of great importance to

the States that only this Court can answer. ....... 13

II. The D.C. Circuit’s expansive view of EPA’s off-cycle

revision power warrants review. ......................... 16

III. The D.C. Circuit’s holding that EPA is barred from

considering the costs and feasibility of an early

NAAQS revision warrants review. ...................... 27

CONCLUSION .......................................................... 32

vi

APPENDIX

Appendix A: Opinion, United States Court of

Appeals for the District of Columbia Circuit,

June 26, 2026………………………...……………..1a

Appendix B: Reconsideration of the National

Ambient Air Quality Standards for Particulate Matter, 89 Fed. Reg. 16202

(March 6, 2024)………………………….………...39a

Appendix C:

Primary Statutes………………………...…...….899a

vii

TABLE OF AUTHORITIES

Cases

Alaska Dep’t of Envtl. Conservation v. EPA,

540 U.S. 461 (2004) ................................................ 16

Almendarez-Torres v. United States,

523 U.S. 224 (1998) ................................................ 30

Am. Farm Bureau Fed’n v. EPA,

559 F.3d 512, (D.C. Cir. 2009) ..................... 5, 19, 23

Am. Trucking Ass’ns, Inc. v. EPA,

175 F.3d 1027 (D.C. Cir. 1999) .............................. 19

Am. Trucking Ass’ns, Inc. v. EPA,

283 F.3d 355 (D.C. Cir. 2002) ................................ 19

Arizona v. EPA,

77 F.4th 1126 (D.C. Cir. 2023) ................................ 9

City of Arlington v. FCC,

569 U.S. 290 (2013) ................................................ 17

Clark v. Sweeney,

607 U.S. 7 (2025) .................................................... 26

Dep’t of Commerce v. New York,

588 U.S. 752, 783 (2019) ........................................ 22

Duncan v. Walker,

533 U.S. 167 (2001) ................................................ 27

Encino Motorcars, LLC v. Navarro,

579 U.S. 211 (2016) ................................................ 22

viii

Entergy Corp. v. Riverkeeper, Inc.,

556 U.S. 208 (2009) ................................................ 29

Env’t Def. Fund v. Thomas,

870 F.2d 892 (2d Cir. 1989) ................................... 29

EPA v. EME Homer City Generation, L.P.,

572 U.S. 489 (2014) .......................................... 14, 16

FCC v. Consumers’ Research,

606 U.S. 656 (2025) ................................................ 30

FCC v. Fox Television Stations, Inc.,

556 U.S. 502 (2009) ................................................ 23

FDA v. Wages & White Lion Investments, L.L.C.,

604 U.S. 542 (2025) ................................................ 25

Indus. Union Dep’t, AFL-CIO v. Am. Petroleum Inst.,

448 U.S. 607 (1980) ................................................ 30

J.W. Hampton, Jr. & Co. v. United States,

276 U.S. 394 (1928) ................................................ 30

Loper Bright Enters. v. Raimondo,

603 U.S. 369 (2024) ................................................ 24

Massachusetts v. EPA,

549 U.S. 497 (2007) ................................................ 16

Mellouli v. Lynch,

575 U.S. 798 (2015) ................................................ 18

Michigan v. EPA,

576 U.S. 743 (2015) .............................. 16, 28, 29, 32

ix

Miss. Comm’n on Env’t Quality v. EPA,

790 F.3d 138 (D.C. Cir. 2015) .................................. 7

Mississippi v. EPA,

744 F.3d 1334 (D.C. Cir. 2013) .................... 5, 19, 29

Motor Vehicle Mfrs. Ass’n v. State Farm Mut. Auto

Ins., 463 U.S. 29 (1983).......................................... 28

Murray Energy Corp. v. EPA,

936 F.3d 597 (D.C. Cir. 2019) .................................. 5

N. Air Cargo v. USPS,

674 F.3d 852 (D.C. Cir. 2012) ................................. 25

Nat’l Ass’n of Mfrs. v. EPA,

750 F.3d 921 (D.C. Cir. 2014) ........................ 5, 8, 23

Ohio v. EPA,

603 U.S. 279 (2024) ............................................ 6, 16

RadLAX Gateway Hotel, LLC v. Amalgamated Bank,

566 U.S. 639 (2012) ................................................ 26

Ross v. Blake,

578 U.S. 632 (2016) ................................................ 26

SEC v. Chenery Corp. (Chenery I),

318 U.S. 80 (1943) .................................................. 25

SEC v. Chenery Corp. (Chenery II),

332 U.S. 194 (1947) ................................................ 25

Union Elec. Co. v. EPA,

427 U.S. 246 (1976) ................................................ 13

x

United States v. Donovan,

429 U.S. 413 (1977) ................................................ 16

United States v. Sineneng-Smith,

590 U.S. 371 (2020) ................................................ 25

Util. Air Reg. Grp. v. EPA,

573 U.S. 302 (2014) .......................................... 16, 18

West Virginia v. EPA,

362 F.3d 861 (D.C. Cir. 2004) ................................ 15

West Virginia v. EPA,

597 U.S. 697 (2022) .................................... 16, 31, 32

White Stallion Energy Ctr., LLC v. EPA,

748 F.3d 1222 (D.C. Cir. 2014) .............................. 28

Whitman v. Am. Trucking Ass’ns,

531 U.S. 457 (2001) ........................ 13, 16, 29, 30, 31

Statutes

28 U.S.C. § 1254(1) ..................................................... 3

42 U.S.C.

§ 7407(a) ............................................................... 6, 7

§ 7407(d) ................................................................... 6

§ 7408 ..................................................... 4, 17, 21, 22

§ 7409(a) ................................................................... 4

§ 7409(b)(1) ....................................................... 17, 27

§ 7409(d)(1) ........................................ i, 1, 4, 5, 17, 27

§ 7410(a) ................................................................... 7

§ 7471 ....................................................................... 7

§ 7607(b)(1) .......................................................... 3, 4

xi

§ 7502 ....................................................................... 7

§ 7513a ..................................................................... 7

Other Authorities

Arthur Fraas, Observations on OIRA's Policies and

Procedures, 63 Admin. L. Rev. 79 (2011) .............. 14

Regulations

85 Fed. Reg. 82684, 82695 (Dec. 18, 2020) ........... 8, 23

Executive Orders

86 Fed. Reg. 7037 (Jan. 25, 2021) ......................... 9, 22

86 Fed. Reg. 7619 (Jan. 27, 2021) ............................... 9

1

INTRODUCTION

Few, if any, federal regulatory regimes touch more

lives than the air-quality standards that EPA sets

under the Clean Air Act. Given their sweeping impact, one might expect the agency to act with special

care when it sets those standards. But under the decision here, EPA can now launch a premature review

of air-quality standards and quickly rewrite them

without undertaking the “thorough review” the Act

normally demands. And in the D.C. Circuit’s view,

EPA cannot consider the inevitably massive consequences of any new standards when deciding whether

to make these off-cycle revisions to NAAQS.

Congress did not grant EPA such unbounded discretion. Under the Clean Air Act, EPA can revise

NAAQS only after “a thorough review” of existing airquality criteria and a decision that the revision would

“be appropriate.” 42 U.S.C. § 7409(d)(1). To be sure,

the Act allows for revisions outside the mandatory

five-year cycle. See id. But it nowhere allows the

agency to use off-cycle revisions to evade congressional constraints and impose NAAQS that result

from a less rigorous assessment of current conditions.

It makes sense that Congress requires EPA to conduct a thorough review every time it revises NAAQS.

As NAAQS lower, the uncertainty in scientific evidence about the public-health effects of exposure

heightens. App. 118a–119a. So do the costs of attaining the lowered standards. How best to balance that

uncertainty against those consequences is a linedrawing decision that cannot be made lightly.

In 2024, EPA took the unprecedented step of finalizing an off-cycle revision without a thorough review.

2

The result was the most stringent PM2.5 NAAQS ever,

tightening the annual standard from 12 to 9 µg/m³.

That single change starts a chain of obligations that

runs for years and saddles the States with crushing

expense. The Commonwealth of Kentucky, the State

of West Virginia, and a coalition of 23 States and one

State environmental agency (State Petitioners),

alongside several industry and other affected parties,

therefore filed petitions for review challenging EPA’s

choice to dispense with the usual process.

Later, even EPA admitted that it had misinterpreted the Clean Air Act, agreeing with the petitioners that section 109(d)(1) does not allow for revision

without a thorough review. It also recognized that

any off-cycle review must consider the consequences

of that revision—something it failed to do in 2024.

Despite EPA’s confession—and against the weight

of 50 years of NAAQS-setting experience—the D.C.

Circuit approved EPA’s now-abandoned view that the

Clean Air Act vests EPA with broad authority to

make early NAAQS revisions without a thorough review. EPA can now avoid its most important statutory guardrails if it acts sooner than the statute requires. And when it does so, it cannot even consider

the costs and feasibility of the NAAQS revision that

results.

The D.C. Circuit’s view of the statute cannot be

the law. It grants a level of discretion that frustrates

the constraints Congress set, turning a thorough review into a passing one. And it gives changing policy

views—rather than the results of a rigorous scientific

review—undue weight in the decision to revise

3

NAAQS. EPA should make its most important regulatory decisions only after it follows the rigorous process Congress established.

This Court should intervene to prevent the D.C.

Circuit’s error from being the last word on the statutory questions presented here. The Clean Air Act

channels review of nationally applicable regulations

exclusively to the D.C. Circuit, 42 U.S.C. § 7607(b)(1),

and no other circuit will have a chance to consider

these issues of surpassing importance. Nor can any

future rulemaking dislodge the decision below, so this

view will bind this administration and every one that

follows. What’s more, if the D.C. Circuit were right on

the statute, granting EPA wide-ranging, unconstrained decisionmaking authority of the sort the

D.C. Circuit envisioned raises serious constitutional

questions. The correct interpretation of the Clean Air

Act avoids those concerns.

State Petitioners thus request that the Court

grant the petition for writ of certiorari.

OPINIONS BELOW

The opinion of the court of appeals (App. 1a–38a)

is reported at 179 F.4th 963 (D.C. Cir. 2026). The

EPA order under review (App. 39a–898a) is available

at 89 Fed. Reg. 16202 (Mar. 6, 2024).

JURISDICTION

The court of appeals entered judgment on June 26,

2026. This Court has jurisdiction under 28 U.S.C.

§ 1254(1).

4

STATUTORY PROVISIONS INVOLVED

The relevant statutory provisions are reproduced

in the appendix to this petition. App. 899a–903a.

STATEMENT OF THE CASE

I. EPA sets air-quality standards, and States implement them.

1. The Clean Air Act requires EPA, through its

Administrator, to determine what air pollutants “may

reasonably be anticipated to endanger public health or

welfare.” 42 U.S.C. § 7408(a)(1)(A). The products of

those determinations—called “air quality criteria”—

must “accurately reflect the latest scientific

knowledge useful in indicating the kind and extent of

all identifiable effects on public health or welfare

which may be expected” from the pollutant. 42 U.S.C.

§ 7408(a)(2).

Once EPA identifies a pollutant and issues airquality criteria, it must propose a NAAQS for that pollutant. 42 U.S.C. § 7409(a). Primary NAAQS—the

kind at issue here—are “ambient air quality standards

the attainment and maintenance of which in the judgment of the Administrator, based on such criteria and

allowing an adequate margin of safety, are requisite

to protect the public health.” 42 U.S.C. § 7409(b)(1).

Both the air-quality criteria and the NAAQS are

subject to “a thorough review” every five years. 42

U.S.C. § 7409(d)(1). After that “thorough review,” EPA

“shall make such revisions in such criteria and standards and promulgate such new standards as may be

appropriate” under sections 108 and 109(b). Id. A

“thorough review” contemplates that the agency will

5

evaluate “the entire body of scientific evidence available.” Murray Energy Corp. v. EPA, 936 F.3d 597, 609

(D.C. Cir. 2019); see also, e.g., Mississippi v. EPA, 744

F.3d 1334, 1344 (D.C. Cir. 2013) (“EPA relied on a

broad array of scientific studies, quantified models,

and input from [the Clean Air Scientific Advisory

Committee (CASAC)], EPA staff, and commenters.”).

EPA can also “review and revise criteria or promulgate new standards earlier or more frequently than

required under this paragraph,” referring to section

109(d). 42 U.S.C. § 7409(d)(1).

2. This petition concerns particulate matter (PM),

“a shorthand for a variety of substances that form particles in the ambient air.” Nat’l Ass’n of Mfrs. v. EPA,

750 F.3d 921, 923 (D.C. Cir. 2014) (NAM). EPA regulates two categories of PM. The type at issue here,

PM2.5, has a diameter under 2.5 micrometers—much

smaller than the diameter of a human hair. App. 66a.

In 2022, EPA concluded that a plurality of PM2.5 (44%)

comes from wildland fires. App. 96a. Other sources of

PM are dust, agriculture, stationary fuel combustion,

industrial processes, and mobile vehicles. App. 95a–

96a. Its specific components (and its potential effects)

vary across the United States. App. 103a–106a.

EPA first issued air-quality criteria and set a

NAAQS for PM in 1971, but it did not target PM2.5 specifically until 1997. Am. Farm Bureau Fed’n v. EPA,

559 F.3d 512, 516–17 (D.C. Cir. 2009). That 1997 proceeding set the NAAQS at 15 µg/m3, see id. at 517,

which EPA lowered to 12 µg/m3 in 2013, see NAM, 750

F.3d at 923. See also App. 66a–73a. In the first two

decades of the 21st century, national average PM2.5

6

concentrations dropped 43% from 13.5 µg/m3 to 7.6

µg/m3. App. 100a.

3. When EPA issues air-quality criteria and sets

NAAQS, States must implement them. 42 U.S.C.

§ 7407(a) (“Each State shall have the primary responsibility for assuring air quality within the entire geographic area comprising such State.”). The shift to

state control at the implementation stage reflects the

Clean Air Act’s cooperative-federalism scheme; the

“Act envisions States and the federal government

working together to improve air quality.” Ohio v. EPA,

603 U.S. 279, 283 (2024). But implementation is a

complicated process involving multiple time consuming (and costly) steps.

The starting point for implementation is designation of geographic areas as “attainment”—within the

relevant NAAQS—or “nonattainment”—either above

the allowable level or contributing to nonattainment

in a “nearby area.” 42 U.S.C. §§ 7407(d)(1)(A), (B). After the NAAQS is set or revised, States have one year

to submit initial area designations to EPA. 42 U.S.C.

§ 7407(d)(1)(A). (That deadline here was February 7,

2025). EPA then adopts or modifies those initial designations. 42 U.S.C. § 7407(d)(1)(B)(i)–(ii). (A district

court ordered that to happen here by February 6,

2027. See All. of Nurses for Healthy Envts. v. Zeldin,

No. 26-cv-03118 (N.D. Cal. July 17, 2026)). If EPA

modifies the initial designations, the States have 120

days to respond before finalization. 42 U.S.C.

§ 7407(d)(1)(B)(ii).

Once EPA issues final designations, States must

prepare state implementation plans (SIPs) explaining

7

how they’ll maintain attainment in any attainment areas or achieve attainment in any non-attainment areas. 42 U.S.C. §§ 7407(a); 7410(a)(1). The Clean Air

Act requires multiple types of SIP revisions. One is an

infrastructure SIP, which evaluates and certifies that

a State is in compliance with the Act. See 42 U.S.C.

§ 7410(a)(2). States must also prepare interstate

transport SIPs to address whether emissions contribute to nonattainment or interfere with maintenance in

another State. See 42 U.S.C. § 7410(a)(2)(D)(i)(I).

Those obligations of course change depending on the

designations EPA issues.

If an area is in attainment, a SIP must “contain

emission limitations and such other measures as may

be necessary . . . to prevent significant deterioration of

air quality.” 42 U.S.C. § 7471. But if an area is in nonattainment, States owe EPA another SIP with a nonattainment plan within 18 months. 42 U.S.C.

§§ 7513a(a)(2), 7410(a)(2)(I). States with nonattainment areas must use “all reasonably available control

measures” and “reasonably available control technology” to achieve attainment within a statutory deadline. 42 U.S.C. §§ 7502(a)(2)(A), (c)(1). Compliance “often mean[s]” using “potentially expensive technology

or expensive process changes to reduce pollution levels” quickly. Miss. Comm’n on Env’t Quality v. EPA,

790 F.3d 138, 146 (D.C. Cir. 2015).

Another immediate burden on States and industry

from a new NAAQS is permitting. Although the designation and SIP revision process takes time, EPA made

permitting obligations kick in immediately. App.

753a. So after a NAAQS revision, any modifications,

new construction, or renewals must go through a timeconsuming and costly permitting process to ensure

8

compliance with the lowered NAAQS. That’s true for

future applications and applications pending when the

2024 Rule was finalized. App. 753a. And if the State

identifies an exceedance with a project, nearby projects will need to update their permits in turn. The result makes economic development more complicated

for all involved.

II. In 2024, EPA decided to revise the NAAQS for

PM ahead of schedule and without a thorough review.

1. The petitions here find their roots in EPA’s

2020 decision to retain the PM2.5 NAAQS set at 12

µg/m3 in 2013. App. 48a. EPA chose that standard in

2013 after population-level studies “reported statistically significant associations between adverse health

effects and [PM] exposure at concentrations between

12.8 and 14.8 µg/m3.” NAM, 750 F.3d at 923 (citation

omitted). It chose air-quality standards at the low end

of those distributions. 85 Fed. Reg. 82684, 82695 (Dec.

18, 2020). But “uncertainties remaining in the scientific evidence” kept EPA from setting a standard below

12 µg/m3. Id. Those “important uncertainties and limitations . . . remain[ed] in the epidemiological evidence” in 2020. Id. at 82714. Plus, recent “scientific

evidence” did not cause EPA to doubt the 2013 standard—even with the uncertain evidence factored in. Id.

at 82717–18. So EPA retained the 2013 standards. Id.

at 82718.

2. That 2020 decision came at the end of the first

Trump Administration. But just weeks later, the new

Administration upended the decision to hold PM2.5

NAAQS steady in the face of scientific uncertainty.

9

The opening salvo was the now-withdrawn Executive Order 14008, which directed a “government-wide

approach” to “combat the climate crisis with bold, progressive action” involving “the full capacity of the Federal Government.” 86 Fed. Reg. 7619, 7622 (Jan. 27,

2021). Another directive, Executive Order 13990, ordered “federal agencies to consider whether Trumpera rules fit the new administration’s agenda.” Arizona v. EPA, 77 F.4th 1126, 1128 (D.C. Cir. 2023) (citing 86 Fed. Reg. 7037, 7037 (Jan. 25, 2021)). That new

agenda included “advanc[ing] environmental justice”

and “confront[ing] the climate crisis.” 86 Fed. Reg. at

7037. At EPA alone, President Biden directed that 48

rules be reviewed under Executive Order 13990.

That list of decisions to review included the 2020

rule retaining the 2013 PM2.5 NAAQS. App. 79a. EPA

announced its decision to reconsider the 2020 rule less

than six months later. Id.

The reconsideration process sharply departed from

the “thorough review” that section 109(d)(1) requires.

Rather than start its scientific analysis anew, as EPA

did for the 2020 rule, EPA supplemented its 2019 Integrated Science Assessment (ISA)—the document

that gathers and evaluates the relevant science—and

updated its Policy Assessment. App. 82a–83a. The

2019 ISA ostensibly remained “the broad scientific

foundation” for EPA’s analysis. App. 136a. EPA’s supplement simply evaluated “some studies that became

available after the literature cutoff date of the 2019

ISA.” App. 84a. EPA chose “not to reassess areas” that

it assumed, based on a first-pass review, were “unlikely to have new information.” App. 82a; see also

App. 91a n.28 (EPA evaluated only “recent studies

that [we]re of greatest policy relevance and utility”).

10

Thus, the ISA Supplement had only a “narrow scope”

that did “not encompass the full multidisciplinary evaluation” undertaken in the 2019 ISA. App. 87a; see also

App. 88a (noting that CASAC has said the “targeted

purpose” and “limitation” on scope in the ISA Supplement “would not be appropriate for ISAs generally”).

Little about the evidence about PM2.5’s health effects had changed since 2020. EPA looked at only two

new studies based on data from ground monitors (rather than hybrid studies combining monitor data with

other estimates), only one of which reported mean

PM2.5 concentrations below 12 µg/m3. App. 220a–221a,

figs. 1–2. And it still identified many of the same uncertainties and limitations present in 2020. App. 352a.

Contrary to the 2020 EPA, the then-current EPA

simply decided “to place less weight on these uncertainties.” Id.

3. The result was the 2024 Rule challenged here.

It invoked section 109(d)(1) to revise the PM2.5 NAAQS

from 12 to 9 µg/m3—the most stringent ever—without

conducting a “thorough review.”

In that short-circuited process, EPA weighed the

same “longstanding large body of epidemiological evidence” that it considered in 2020, with the same limitations and uncertainties. App. 352a. Yet this time,

EPA discounted the uncertainties so that it could emphasize studies it gave little weight to in 2020.

Equally important is what EPA did not consider in

its unprecedented revision: its real-world consequences. EPA repeatedly stated that “the economic

and technical feasibility of attaining ambient standards are not to be considered in setting or revising

NAAQS.” App. 763a, 59a, 61a, 64a, 68a, 767a. So EPA

11

offered no response to the significant consequences of

revising the NAAQS down to 9 µg/m3. EPA finalized

the PM2.5 NAAQS in March 2024.

III. Petitioners challenged the 2024 Rule in the

D.C. Circuit

State Petitioners—Kentucky, West Virginia, and

23 other States—filed petitions for review in the D.C.

Circuit challenging the 2024 Rule. Industry groups led

by the Chamber of Commerce filed petitions that the

court of appeals consolidated with the State-led petitions. And 16 more States, several localities, and public-interest groups intervened as respondents to defend the 2024 Rule.

EPA initially defended the 2024 Rule in briefing

and at oral argument. But it ultimately withdrew that

defense and disavowed its asserted reconsideration

authority. EPA admitted that it had not conducted a

“thorough review” but instead had only “supplement[ed]” a “prior review with a limited selection of

additional studies”; it had then “revis[ed] the NAAQS

on that basis alone.” D.C.Cir.Dkt. # 2147050 (Mot. to

Vacate) at 2. The “best reading” of the statute, EPA

admitted, did not permit that approach. Id. at 9. It

thus sought vacatur on two grounds: (1) that it lacked

authority to revise NAAQS without conducting the

“thorough review” that section 109(d)(1) requires, id.

at 10–18, and (2) that, alternatively, its failure to consider costs made its revision arbitrary and capricious,

id. at 18–21.

A panel of the D.C. Circuit denied the consolidated

petitions. It agreed with the defenses EPA abandoned

and adopted an additional statutory holding, now advanced by intervenors.

12

The D.C. Circuit’s primary holding grants EPA unprecedented revision power. The court began by identifying section 109(b) as the source of EPA’s authority

to revise NAAQS off cycle. App. 19a. In its view, that

section does not require a thorough review for off-cycle

revisions. App. 19a, 21a. The court’s theory was suggested for the first time at oral argument by a member

of the panel. And the court embraced it despite EPA’s

admission that its rulemaking relied on section 109(d),

not section 109(b). Section 109(d)(1), the court held,

merely added a five-year review requirement; it “does

not limit the Administrator’s authority to revise a

standard sooner.” App. 20a–21a.

The upshot was that section 109(d)(1) does not “require a ‘thorough review’ as a precondition to an offcycle revision.” App. 21a. The court took that view for

two reasons, one textual and the other policy-based. In

the text, it found dispositive that the word “thorough”

does not appear in section 109(d)(1)’s second sentence.

App. 21a–22a. And it rejected the argument that the

words “review” and “under this paragraph” in that

sentence import the “thorough review” requirement to

off-cycle reviews because it “would stretch [the second

sentence’s] meaning to the point of frustrating it.”

App. 22a–23a. As a policy matter, it viewed the thorough-review requirement as “prevent[ing] the Administrator from responding promptly to changes in the

relevant science.” App. 23a. Applying it to off-cycle reviews would thus “unnecessarily delay promulgation

of a new standard.” Id. So the D.C. Circuit exempted

all off-cycle reviews from the “thorough review” requirement, leaving these NAAQS revisions entirely up

to the agency’s discretion. App. 25a.

13

The court also rejected petitioners’ alternative

claim that the decision whether an off-cycle revision is

“appropriate” should factor in the costs and feasibility

of that revision. App. 28a–33a. According to the court,

“economic considerations and attainability” are impermissible at any step of “the NAAQS-setting process.”

App. 30a.

REASONS TO GRANT THE PETITION

The text of the Clean Air Act does not confer on

EPA the expansive revision authority that the D.C.

Circuit found. That mistaken holding will impose profound harms on the States and the businesses that

fuel their economies. Only this Court can correct it, so

it should grant a writ of certiorari and do so.

I. This case presents questions of great importance to the States that only this Court can

answer.

Before turning to the statutory questions at the

heart of this petition, the Court should consider what’s

at stake here.

NAAQS are the core of EPA’s regulatory bailiwick.

They “are the engine that drives nearly all of Title I of

the [Clean Air Act].” Whitman v. Am. Trucking Ass’ns,

531 U.S. 457, 468 (2001); see also Union Elec. Co. v.

EPA, 427 U.S. 246, 249 (1976) (describing NAAQS implementation as the “heart” of the CAA). No wonder,

then, that NAAQS have such enormous practical consequence; indeed, they “affect the entire national economy.” Whitman, 531 U.S. at 475. One former official

with the White House Office of Information and Regulatory Affairs even declared that “[t]he biggest

rules—the biggest decisions—during [his] almost

14

thirty-year tenure involved the National Ambient Air

Quality Standards.” Arthur Fraas, Observations on

OIRA's Policies and Procedures, 63 Admin. L. Rev. 79,

81 (2011).

The Clean Air Act’s cooperative-federalism design

also hinges on EPA’s initial decision to set or revise

NAAQS. After all, EPA’s adoption of a revised NAAQS

“shifts the burden to States.” EPA v. EME Homer City

Generation, L.P., 572 U.S. 489, 498 (2014). State-level

compliance with those NAAQS through revised SIPs

and permitting all follows from that initial decision.

And States can’t quibble with EPA’s standard-setting

at any of those later stages.

For reasons like these, 41 States—25 petitioners

and 16 intervenors—took a position below on whether

the 2024 Rule is lawful. The two groups don’t agree on

much in this case. But both groups understand that

the 2024 Rule is important enough to justify spending

limited State resources challenging or defending it.

That fact alone should leave no doubt that the questions presented here are of national importance.

At the same time, the D.C. Circuit’s answers to

these questions cause immediate—and local—harms

in each of the States. Just look to some of the evidence

State Petitioners offered below via sworn declarations.

See D.C.Cir.Dkt. #2079737 (State Petitioners’ Opening Br. Add.). For initial area designations alone,

States had to collectively spend millions of dollars and

thousands of hours of staff time. Id. at 11a–14a, 57a,

74a–75a, 85a, 161a. And those figures look small compared to the time and hours that will be required once

EPA issues its final designations. States expect to face

15

the high costs of developing and implementing nonattainment SIPs, exceptional-events demonstrations,

and related submissions. Id. at 14a–18a, 57a–59a.

63a–66a, 76a–79a, 87a–88a, 94a, 103a–104a, 165a.

And in the areas that could be first-time designees,

States will be forced to train environmental regulators

and conduct outreach on compliance. Id. at 16a, 58a,

75a–76a, 102a. Finally, permitting across the country

has already become more difficult under the 2024

Rule, see id. at 18a–20a, 66a–67a, 79a–80a, 166a–

168a, 216a–217a, hamstringing new development and

construction that brings new jobs to States.

Many of these harms are immediate. States have

already submitted initial designations, they are currently required to apply the 2024 Rule to pending permits, and many are preparing for the impending SIP

revision process. Some of the costliest obligations, like

responding to the designations and revising SIPs, are

looming. There is little doubt that States’ obligations

have become “more difficult and onerous,” West Virginia v. EPA, 362 F.3d 861, 868 (D.C. Cir. 2004), under

the 2024 Rule, with matters growing worse as EPA

takes more steps to implement the NAAQS. These immediate and impending burdens justify this Court’s

quick intervention to correct the D.C. Circuit’s mistaken interpretation of the Clean Air Act.

To summarize, the questions presented here are

significant enough for 41 States to have chimed in on

one side or the other below. They are causing real

harm to States across the nation. And going forward,

EPA can use ad hoc reconsiderations to impose similar

harms without undertaking the thorough review the

statute requires. That new—and flawed—framework

will upset the Clean Air Act’s cooperative-federalism

16

scheme. Yet without this Court’s intervention, the D.C.

Circuit will get the first and only say on these weighty

issues. The Clean Air Act requires that petitions like

the ones below be heard in the D.C. Circuit alone. See

42 U.S.C. § 7607(b)(1). There will be no circuit split and

no lower-court percolation of the questions presented.

Only this Court can decide whether the Clean Air Act

provides EPA with a shortcut to off-cycle NAAQS revisions that is blind to costs and feasibility.

This Court in recent history has not hesitated to

interpret the limits of EPA’s Clean Air Act authority

when called upon. See, e.g., Ohio v. EPA, 603 U.S. 279;

West Virginia v. EPA, 597 U.S. 697 (2022); Michigan

v. EPA, 576 U.S. 743 (2015); Util. Air Reg. Grp. v. EPA,

573 U.S. 302 (2014); EME Homer City, 572 U.S. 489;

Massachusetts v. EPA, 549 U.S. 497 (2007); Alaska

Dep’t of Envtl. Conservation v. EPA, 540 U.S. 461

(2004); Whitman, 531 U.S. 457. This petition once

more “concern[s] the construction of a major federal

statute,” United States v. Donovan, 429 U.S. 413, 422

(1977), and the Court should intervene again here.

II. The D.C. Circuit’s expansive view of EPA’s

off-cycle revision power warrants review.

The Court should also grant the petition because

the D.C. Circuit got the important questions in this

case wrong. It was a mistake to adopt a novel interpretation of the Clean Air Act to provide EPA authority to conduct an off-cycle review free of essential statutory constraints.

1. The first question presented turns on whether

EPA must engage in a “thorough review” of its air-

17

quality criteria and the current NAAQS when it conducts an off-cycle NAAQS revision. The answer is yes,

and this Court should grant this petition to say so.

The Clean Air Act “forecloses” EPA’s “assertion of

authority” in the 2024 Rule. City of Arlington v. FCC,

569 U.S. 290, 301 (2013). It establishes a five-year cycle within which EPA must “complete a thorough review of” its air-quality criteria and “the [NAAQS]

promulgated” by EPA. 42 U.S.C. § 7409(d)(1). Only after undertaking that comprehensive review can EPA

“make such revisions in such criteria and standards

and promulgate such new standards as may be appropriate in accordance with [section 108] and [section

109(b)].” Id. In other words, the “thorough review” operates as a condition precedent to standard-setting.

Further, the two cross-referenced sections establish

the process for issuing air-quality criteria and setting

NAAQS. The first requires EPA to issue air-quality

criteria that “accurately reflect the latest scientific

knowledge.” 42 U.S.C. § 7408(a)(2). And the second requires EPA to issue NAAQS that, “allowing an adequate margin of safety, are requisite to protect the

public health.” 42 U.S.C. § 7409(b)(1). So in multiple

places and in multiple ways, the statute stresses that

EPA’s NAAQS decision must start from an evidencebased, science-backed, and comprehensive record.

Beyond the mandatory five-year review, EPA can

also “review and revise criteria or promulgate new

standards earlier or more frequently than required

under this paragraph.” 42 U.S.C. § 7409(d)(1). But petitioners and ultimately EPA agreed below that EPA

still must undertake a “thorough review” when it conducts such an off-cycle revision. In contrast, the D.C.

18

Circuit determined that EPA can engage in a less rigorous (yet undefined) form of review during an off-cycle revision mostly because the second sentence of section 109(d)(1) doesn’t repeat the word “thorough.” App.

21a–22a. In other words, it found sweeping agency authority in supposed congressional silence.

In context, the D.C. Circuit’s reading is wrong. See

Util. Air Reg. Grp., 573 U.S. at 321 (“[R]easonable

statutory interpretation must account for both ‘the

specific context in which language is used’ and ‘the

broader context of the statute as a whole.” (citation

omitted) (cleaned up)). Section 109(d)(1)’s second sentence references the “thorough review” process with

the phrase “under this paragraph.” It thus speaks to

the timing of the review process; it does not dilute the

substance of that process or implicitly redefine “review.” The two sentences cannot be read in isolation.

Section 109(d)(1)’s second sentence gives EPA more

opportunities to revise NAAQS, but it does not give it

the power to conduct a short-circuited reconsideration

process.

Make no mistake, the off-cycle revision authority

that the D.C. Circuit found in sections 109(b) and

(d)(1) lacks meaningful guardrails. The ultimate decision is the same whether EPA acts on- or off-cycle, and

“[s]tatutes should be interpreted as a symmetrical and

coherent regulatory scheme.” Mellouli v. Lynch, 575

U.S. 798, 809 (2015) (citation omitted). But the D.C.

Circuit’s novel shortcut allows one Administrator,

faced with facts and data without significant changes,

to quickly reverse another Administrator’s decision

based on a new judgment alone—just what happened

here. App. 354a. That level of discretion frustrates the

statutory constraints set by Congress, as it effectively

19

renders the bounded, mandatory five-year process an

empty formality that can quickly be mooted by an unbounded, discretionary, off-cycle review.

The D.C. Circuit responded to petitioners’ objection

to the scope of EPA’s newfound power by pointing to

the Clean Air Act’s “substantive standard” and its “requirement of reasoned decisionmaking.” App. 25a; see

also id. (“Those requirements are not toothless and

have been applied by this court when reviewing

NAAQS on many occasions.”). To be sure, the D.C. Circuit has rejected a decision to retain a NAAQS. Am.

Farm Bureau Fed’n, 559 F.3d at 519–26. And it has

rejected parts of rulemakings (including secondary

standards) containing NAAQS revisions. Id. at 528–

31; Mississippi, 744 F.3d at 1358–62; Am. Trucking

Ass’ns, Inc. v. EPA, 283 F.3d 355, 361–362 (D.C. Cir.

2002). Yet the court below offered no example of the

D.C. Circuit vacating a decision to tighten a primary

NAAQS as substantively arbitrary and capricious—

because none exists.1 In a regulatory landscape in

which EPA already has broad discretion given the scientific judgment call at the heart of the process, the

arbitrary-and-capricious standard does little to remedy the removal of a key statutory constraint. Put an-

1 When EPA first chose to regulate PM2.5, the D.C. Circuit re-

jected the retention of PM10 as an indicator because EPA failed

to explain how it would avoid potential “‘double regulation’ of the

PM2.5 component of PM10 and potential underregulation of the

PM10–2.5 component.” Am. Trucking Ass’ns, Inc. v. EPA, 175 F.3d

1027, 1054 (D.C. Cir. 1999). But the D.C. Circuit later approved

the same indicator after EPA “cured that failure of explanation

and provided a reasonable rationale for its choice of PM10.” Am.

Farm Bureau Fed’n, 559 F.3d at 535–36.

20

other way, the general backstop of arbitrary-and-capricious review does not forgive the D.C. Circuit’s statutory error.

2. The D.C. Circuit made much of the notion that

EPA must “respond[] promptly to changes in the relevant science” and claimed that “[t]his case illustrates

the problem.” App. 23a. But the facts here—and the

reality of NAAQS-setting generally—belies any suggestion that the Clean Air Act was meant to provide

EPA with a shortcut to a NAAQS revision through an

off-cycle revision.

In the court’s view, just months after the 2020 Action, EPA “became aware of certain scientific studies

likely to require a change in the standard for fine particulate matter and began updating its science and

policy assessments.” App. 23a. But that overstates the

need for prompt action here. The NAAQS were not crying out for an immediate response because of urgent

scientific evidence “requir[ing] a change.” Id. Indeed,

a closer look at what EPA relied on reveals that little

“changed” about the “existing corpus of scientific

knowledge.” App. 272a.

Recall that EPA’s only addition in the 2024 Rule

was a supplemental ISA that evaluated “some studies

that became available after the literature cutoff date

of the 2019 ISA.” App. 84a. They included studies with

“alternative methods” to control for outside variables,

experimental studies about cardiovascular effects,

studies exploring evidence of race or socioeconomic

risk disparities, and studies focused on COVID-19.

App. 136a–140a. Yet EPA found the evidence in several of those categories inconclusive or too uncertain.

21

App. 183a, 195a–196a. And for the most important epidemiological studies, EPA’s data shed little new light

on whether the current NAAQS were appropriate.

App. 220a–221a, figs. 1–2. So the court below was

wrong to assert that the 2024 Rule responded to some

urgent update to scientific knowledge.

It’s also difficult to see how avoiding the thoroughreview process is necessary to respond to new science.

Section 108 requires that EPA’s air-quality criteria

“accurately reflect the latest scientific knowledge.” 42

U.S.C. § 7408(a)(2). Requiring EPA to conduct a thorough review of its air-quality criteria is the best way

to guarantee that the NAAQS-setting process is consistent with updated science, rather than a rushed and

skewed half-picture of the relevant field.

Still, the D.C. Circuit’s assumption that latebreaking scientific studies could ever “require” a

NAAQS revision doesn’t line up with the NAAQS-setting process. When EPA answers the Clean Air Act’s

public-health question, “the available health effects

evidence . . . reflects a continuum, consisting of levels

at which scientists generally agree that health effects

are likely to occur, through lower levels at which the

likelihood and magnitude of the response become increasingly uncertain.” App. 118a–119a.

In other words, EPA’s line-drawing decision gets

tougher as the NAAQS gets closer to zero because the

health consequences are far less obvious and far more

difficult to trace to a specific type of pollutant. So the

notion that a few studies could “require” significant revisions doesn’t track reality. Indeed, that’s not how

EPA framed its decision here. In the 2024 Rule, the

uncertainties present in 2020 remained—EPA simply

22

decided “to place less weight on these uncertainties.”

App. 352a. The key difference was in the Administrator’s judgment, based on nearly identical facts and

data. Id.

The more obvious change was thus political, not

scientific. A new President with a different agenda

hired new EPA leadership with a different view of the

uncertainties inherent in the NAAQS-setting decision.

As the 2024 Rule explains, they immediately got to

work reconsidering “certain agency actions” like “the

2020 Particulate Matter NAAQS Decision.” App. 79a

(citing EO 13990). Those reconsiderations were part of

the previous Administration’s larger effort to “confront” what it called “the climate crisis.” EO 13990, 86

Fed. Reg. at 7037.

New leadership with new ideas is expected. Dep’t

of Commerce v. New York, 588 U.S. 752, 783 (2019) (“It

is hardly improper for an agency head to come into office with policy preferences and ideas.”). And to be

clear, the Clean Air Act leaves room for EPA to exercise its discretion in different ways. But it also requires that the NAAQS be informed by “the latest scientific knowledge.” 42 U.S.C. § 7408(a)(2). To that

end, it requires every Administrator, no matter how

they approach NAAQS-setting, to engage in a “thorough review” of the scientific evidence before promulgating major regulatory changes.

This approach provides certainty for States and

businesses. All agree that “longstanding policies” can

“creat[e] serious reliance interests,” Encino Motorcars,

LLC v. Navarro, 579 U.S. 211, 222 (2016) (quoting

FCC v. Fox Television Stations, Inc., 556 U.S. 502, 515

23

(2009)), and EPA’s well-settled practice of only revising NAAQS after a thorough review and on the fiveyear cycle no doubt fits that bill. And enforcing the

thorough-review requirement for all revisions does not

mean that off-cycle revisions can never happen. As

was the case in the five decades before the 2024 Rule,

it simply makes off-cycle review rare.

By forcing regulatory rigor, the Clean Air Act’s

thorough-review process ensures that NAAQS revisions are rooted in science, not in politics. That, in

turn, ensures that NAAQS revisions (and the compliance deadlines that follow) are not made quickly or

lightly. That does not frustrate the Act’s purpose. It is

the best-case scenario for States that must implement

the NAAQS and the regulated entities that must comply with them.

3. The D.C. Circuit’s statutory holding was mistaken, and its policy justifications for the holding only

expose its flaws. A final problem with the decision below further justifies this Court’s review: it gives EPA

a power it has expressly disclaimed.

When the 2024 Rule was promulgated, EPA viewed

section 109(d)(1) as “providing additional” and “independent” authority allowing revisions without a thorough review. Response to Comments 122. That was a

marked departure from past practice. Each of its prior

PM decisions was made after a thorough review, on

(and often behind) the five-year schedule. See Am.

Farm Bureau Fed’n, 559 F.3d at 516–18 (describing

the 1997 and 2006 processes); NAM, 750 F.3d at 923

(describing the 2013 process); 85 Fed. Reg. at 82689

(describing the 2020 process). EPA sought in 2009 to

24

reconsider the ozone NAAQS, but it tabled the question before finalization. Letter from C. Sunstein to L.

Jackson (Sept. 2, 2011).2 And it more recently abandoned a reconsideration of the ozone NAAQS in favor

of a “full and complete review.” EPA Initiates New Review of the Ozone NAAQS to Reflect the Latest Science,

EPA (Aug. 21, 2023).3 EPA realigned its statutory

views with that past practice when it confessed error

below.

The D.C. Circuit should have at least considered

that “longstanding practice of the government” as an

interpretive tool. Loper Bright Enters. v. Raimondo,

603 U.S. 369, 386 (2024) (citation omitted). The “independent judgment” is left to the court, but “[c]areful

attention to the judgment of the Executive Branch

may help” that effort. Id. at 412–13. The court of appeals instead held that a different provision—section

109(b)—provides all the revision authority EPA

needed here. App. 19a–21a. It did so on its own initiative, embracing a theory raised for the first time at

oral argument by a member of the panel.

Looking to section 109(b) was a mistake for a few

reasons. For one, EPA never relied on section 109(b)

as a source of independent revision authority. That

lack of reliance was already clear from the 2024 Rule

and the briefs below, but EPA left no doubt when it

moved to vacate the 2024 Rule. That means that the

D.C. Circuit should not have reached the section

109(b) issue.

2 Available at https://perma.cc/G9WN-LGH7.

3 Available at https://perma.cc/ZPG7-YGXS.

25

It is “a simple but fundamental rule of administrative law” that “a reviewing court . . . must judge the

propriety of [agency] action solely by the grounds invoked by the agency.” SEC v. Chenery Corp., 332 U.S.

194, 196 (1947) (Chenery II). Unless an “agency acted”

under the same authority “upon which its action can

be sustained,” its decision “cannot be upheld.” SEC v.

Chenery Corp., 318 U.S. 80, 95 (1943) (Chenery I). The

Court reaffirmed this “now-bedrock principle” in 2025.

FDA v. Wages & White Lion Investments, L.L.C., 604

U.S. 542, 587 (2025).

EPA never invoked section 109(b) as the source of

its authority to conduct an off-cycle revision without a

thorough review, so the D.C. Circuit was wrong to uphold the 2024 Rule for that reason. To hold otherwise,

the D.C. Circuit exempted all statutory questions from

the Chenery doctrine, citing a line of circuit precedent.

App. 20a n.5. That court’s precedent is muddled on this

question. See, e.g., N. Air Cargo v. USPS, 674 F.3d 852,

860 (D.C. Cir. 2012) (“[W]e have held that [the Chenery

doctrine] applies to statutory interpretations.”). Thankfully, this Court’s precedent is clear. It recently held

that getting “the governing law” wrong does not excuse

an agency’s failure to raise an issue. Wages & White

Lion, 604 U.S. at 591. So the D.C. Circuit should not

have engaged on this unpreserved issue.

To compound its error, the lower court also violated

the party-presentation principle when it adopted an

argument that EPA never raised. If a party fails to

make an “argument entitling [it] to relief,” a court

should not make and sustain that argument itself.

United States v. Sineneng-Smith, 590 U.S. 371, 375–

76 (2020). This Court has again made clear recently

that “courts call balls and strikes; they don’t get a turn

26

at bat.” Clark v. Sweeney, 607 U.S. 7, 9 (2025) (citation

omitted).

Finally, even if the court of appeals was right to

reach the merits of section 109(b), it reached the

wrong result. In its view, “nothing in [section]

7409(d)(1) displaces the Administrator’s revision authority in [section] 7409(b).” App. 21a. The thoroughreview requirement, in other words, does not apply to

a revision under section 109(b). But that conclusion requires overlooking the rule that when “a general authorization and a more limited, specific authorization

exist side-by-side,” the “terms of the specific authorization must be complied with.” RadLAX Gateway Hotel, LLC v. Amalgamated Bank, 566 U.S. 639, 645

(2012).

An alternative approach renders the specific provision superfluous, id., as the D.C. Circuit did in the offcycle revision context below. That approach suggests

that the Clean Air Act’s NAAQS-setting provisions

were not enacted as a single statutory scheme. But

Congress in sections 109(b) and 109(d) did just the opposite—section 109(d)(1) requires a thorough review

before EPA sets the substantive standard defined in

section 109(b). And section 109(b) authorizes revisions

“in the same manner as promulgated.”

The D.C. Circuit’s conclusion also requires ignoring

that “[w]hen Congress amends legislation, courts

must presume it intends the change to have real and

substantial effect.” Ross v. Blake, 578 U.S. 632, 641–

42 (2016) (cleaned up). Applied here, a court should

presume that the 1977 amendments updated the statutory scheme to add section 109(d)(1)’s substantive requirements to section 109(b)’s pre-existing process.

27

***

EPA was right below to abandon a novel interpretation of the Clean Air Act that claimed vast discretion

to conduct an off-cycle NAAQS revision with less than

a thorough review of the scientific evidence. But that

abandoned approach is now the law in the D.C. Circuit, the only court of appeals that judges the limits of

EPA’s NAAQS-setting authority. The Court should

step in to correct these errors.

III. The D.C. Circuit’s holding that EPA is barred

from considering the costs and feasibility of

an early NAAQS revision warrants review.

Even if the Court is inclined to agree with the D.C.

Circuit’s statutory holding, it should grant this petition to clarify what considerations must underlie a

reasoned decision. In particular, it should make clear

that costs and feasibility are relevant when EPA decides whether to conduct an off-cycle NAAQS revision.

1. As with above, the best starting point is the

Clean Air Act’s text. Section 109(d)(1) allows EPA to

revise a NAAQS only “as may be appropriate.” 42

U.S.C. § 7409(d)(1). That appropriateness inquiry,

tied to the decision whether to revise a NAAQS, is distinct from the inquiry tied to the ultimate NAAQS-setting decision. In that separate context, section 109(b)

requires that NAAQS be set at a level “requisite to protect the public health” with “an adequate margin of

safety.” 42 U.S.C. § 7409(b)(1).

Undefined in the text, the word “appropriate” must

have an independent meaning as it applies to a distinct inquiry. See Duncan v. Walker, 533 U.S. 167, 174

(2001) (requiring that courts “give effect, if possible, to

28

every clause and word of a statute” (citation omitted)).

As this Court has held, the word appropriate used

elsewhere in the Clear Air Act is “the classic broad and

all-encompassing term that naturally and traditionally includes consideration of all the relevant factors.”

Michigan, 576 U.S. at 752 (quoting White Stallion Energy Ctr., LLC v. EPA, 748 F.3d 1222, 1266 (D.C. Cir.

2014) (Kavanaugh, J.)). Among those factors, “cost” is

“a centrally relevant factor when deciding whether to

regulate” because “reasonable regulation ordinarily

requires paying attention to the advantages and the

disadvantages of agency decisions.” Id. at 752–53.

Whether it is appropriate to conduct an off-cycle review is thus an inquiry subject to the standard requirements of reasoned decisionmaking. And unless the

statute says otherwise, a reasoned decisionmaker must

consider the costs of his decision. As this Court explained in Michigan, “[o]ne would not say that it is even

rational, never mind ‘appropriate,’ to impose billions of

dollars in economic costs in return for a few dollars in

health or environmental benefits.” Id. at 752.

By these measures, the 2024 Rule was arbitrary

and capricious. Agencies owe an obligation to “examine the relevant data and articulate a satisfactory explanation for its action including a ‘rational connection between the facts found and the choice made.’”

Motor Vehicle Mfrs. Ass’n v. State Farm Mut. Auto

Ins., 463 U.S. 29, 43 (1983) (citation omitted). EPA refused to examine costs at all, much less connect them

to the choice to revise the standard significantly down.

Had it done so, it would have had to grapple with the

profound economic consequences wrought by its early,

off-cycle revision. Because it failed to do so, the 2024

Rule cannot stand.

29

2. To the D.C. Circuit, Whitman and related circuit precedent required rejecting this argument. App.

28a–33a. But Whitman is not dispositive here. That’s

because this Court addressed only whether EPA “may

consider the costs of implementation in setting

[NAAQS] under [section 109(b)(1)].” Whitman, 531

U.S. at 462 (emphasis added). It adopted “the modest

principle that where the Clean Air Act expressly directs EPA to regulate on the basis of a factor that on

its face does not include cost, the Act normally should

not be read as implicitly allowing the Agency to consider cost anyway.” Michigan, 576 U.S. at 755–56; accord Entergy Corp. v. Riverkeeper, Inc., 556 U.S. 208,

223 (2009).

Whitman did not purport to apply to the “threshold

decision to revise the primary NAAQS level,” Mississippi, 744 F.3d at 405—just the NAAQS-setting decision governed by section 109(b)(1)’s substantive standard. 531 U.S. at 465. Importantly, section 109(b)(1)

does not contain the word “appropriate” located in section 109(d)(1). Moreover, it applied to a mandatory oncycle revision, not a discretionary off-cycle review like

here. And it expressly called for an express focus on

public health in a way that section 109(d)(1) does not.

It is thus wrong to assume that the section 109(b) concepts addressed in Whitman apply mechanically to the

distinct context of section 109(d)(1) discretionary revisions. See Env’t Def. Fund v. Thomas, 870 F.2d 892,

898 (2d Cir. 1989) (refusing to read section 109(b) as

imposing implicit limits on revisions under section

109(d)).

This Court should grant review to clarify that

Whitman’s statutory holding is limited to the ultimate

NAAQS-setting decision in an on-cycle revision. And

30

it should make clear to EPA that when it exercises its

discretion to decide whether to conduct an off-cycle review, it must consider costs and feasibility.

3. Even if the D.C. Circuit’s interpretation were

correct, it would raise serious constitutional questions

about the authority Congress delegated to EPA to conduct off-cycle reviews. That’s because it endorses a

sweeping regulatory power without the meaningful

guardrails that come through considering costs and

feasibility. And it’s another good reason for this Court

to reject that interpretation. In general, this Court favors “[a] construction of the statute that avoids this

kind of open-ended grant” and avoids this constitutional problem altogether. See Indus. Union Dep’t,

AFL-CIO v. Am. Petroleum Inst., 448 U.S. 607, 646

(1980) (plurality); see also Almendarez-Torres v.

United States, 523 U.S. 224, 237 (1998) (When “fairly

possible,” courts should interpret statutes “to avoid

not only the conclusion that it is unconstitutional but

also grave doubts upon that score.” (citation omitted)).

This Court’s traditional nondelegation test was described in Whitman itself. At its core, “the constitutional question is whether the statute has delegated

legislative power to the agency.” Whitman, 531 U.S. at

472. For such delegation to be lawful, “Congress must

‘lay down by legislative act an intelligible principle to

which the person or body authorized to act is directed

to conform.” Id. (citing J.W. Hampton, Jr. & Co. v.

United States, 276 U.S. 394, 409 (1928)) (emphasis removed) (cleaned up). As this Court recently confirmed

that “[t]he ‘guidance’ needed is greater . . . when an

agency action will ‘affect the entire national economy.’” FCC v. Consumers’ Research, 606 U.S. 656, 673

(2025) (quoting Whitman, 531 U.S. at 475); see also id.

31

at 721–22 (Gorsuch, J., dissenting) (“Congress must

give far more detailed instructions if it wants an

agency to regulate an entire industry.”).

Under that approach, a statute that confers unfettered discretion to conduct an off-cycle review is unconstitutional. The 2024 Rule is a good example of why

that’s so. EPA steadfastly refused to consider costs, yet

it acknowledged that the Clean Air Act “does not require” EPA to set NAAQS “at a zero-risk level.” App.

414a. EPA thus stated the obvious: there exists a

range at which it could regulate but has decided not

to. See Whitman, 531 U.S. at 475 (discussing EPA’s

“judgments of degree”).

But under the D.C. Circuit’s reading of Whitman,

how future EPAs exercise that judgment is for EPA

alone to know. App. 63a (“The selection of any particular approach to providing an adequate margin of

safety is a policy choice left specifically to the Administrator’s judgment.”). That logic means that EPA has

discretion to revise NAAQS to a zero-risk level, no

matter the implications, if a future Administrator believed that no amount of PM2.5 is safe for the public.

These

are

“basic

and

consequential

tradeoffs . . . that Congress would likely have intended for itself.” West Virginia, 597 U.S. at 730. So it

is simply no longer the case that this sweeping power

“fits comfortably within the scope of discretion permitted by” this Court’s precedent. Whitman, 531 U.S. at

476. The Court should not construe the Clean Air Act

to give EPA discretionary off-cycle review authority

that raises these constitutional concerns.

32

***

The Clean Air Act’s requirement that a NAAQS revision be “appropriate” means that EPA must think

about costs and feasibility when deciding to conduct

an off-cycle NAAQS revision. But if EPA’s only focus

is public health—with no regard for the massive consequences of an off-cycle revision—then this review

process would raise serious constitutional concerns.

CONCLUSION

As is often the case when this Court is asked to interpret EPA’s Clean Air Act authority, see, e.g., Michigan v. EPA, 576 U.S. 743; West Virginia v. EPA, 597

U.S. 697, the questions presented here are deeply important, for distinct reasons, to both States and industry. This petition is thus being filed alongside another

petition filed by industry groups. The Court should

grant both petitions for a writ of certiorari.

33

Respectfully submitted,

JOHN. B. MCCUSKEY

Attorney General

RUSSELL COLEMAN

Attorney General

MICHAEL R. WILLIAMS

Solicitor General

MATTHEW F. KUHN

Solicitor General

Counsel of Record

Office of the

West Virginia

Attorney General

State Capitol Complex

Building 1, Room E-26

Charleston, West

Virginia 25305

(304) 558-2021

mwilliams@wvago.gov

Counsel for the State of

West Virginia

JOHN H. HEYBURN

Principal Deputy

Solicitor General

JACOB M. ABRAHAMSON

Deputy Solicitor General

Office of the Kentucky

Attorney General

1024 Capital Center Drive

Suite 200

Frankfort, Kentucky 40601

(502) 696-5300

Matt.Kuhn@ky.gov

Counsel for the

Commonwealth of Kentucky

34

STEVE MARSHALL

Attorney General

CORI MILLS

Acting Attorney General

A. BARRETT BOWDRE

Solicitor General

Office of the Attorney

General

State of Alabama

501 Washington Avenue

P.O. Box 300152

Montgomery, Alabama

36130-0152

(334) 242-7300

Barrett.Bowdre

@AlabamaAG.gov

JESSICA M. ALLOWAY

Acting Solicitor General

Alaska Department

of Law

1031 West 4th Avenue,

Suite 200

Anchorage, Alaska

99501-1994

(907) 269-6612

Jessie.Alloway

@alaska.gov

Counsel for the State of

Alabama

Counsel for the

State of Alaska

TIM GRIFFIN

Attorney General

JAMES UTHMEIER

Attorney General

AUTUMN H. PATTERSON

Solicitor General

Office of the Arkansas

Attorney General

101 W. Capitol Ave.

Little Rock, Arkansas

72201

(501) 682-2007

Autumn.Patterson

@ArkansasAG.gov

DAVID M.S. DEWHIRST

Solicitor General

Office of the Attorney

General

The Capitol, PL-01

Tallahassee, Florida

32399

(850) 414-3300

David.Dewhirst

@myfloridalegal.com

Counsel for the

State of Arkansas

Counsel for the

State of Florida

35

CHRISTOPHER M. CARR

Attorney General

RAÚL R. LABRADOR

Attorney General

JOHN HENRY THOMPSON

Solicitor General

Office of the Georgia

Attorney General

40 Capitol Square, SW

Atlanta, Georgia 30334

(404) 458-3373

jhthompson@law.ga.gov

MICHAEL ZARIAN

Solicitor General

Office of the Idaho

Attorney General

P.O. Box 83720

Boise, Idaho 83720-0010

(208) 334-2400

Michael.Zarian

@ag.idaho.gov

Counsel for the

State of Georgia

Counsel for the

State of Idaho

THEODORE E. ROKITA

Attorney General

BRENNA BIRD

Attorney General

JAMES A. BARTA

Solicitor General

Office of the Attorney

General

IGC South, Fifth Floor

302 West Washington

Street

Indianapolis, Indiana

46204

(317) 232-0709

James.Barta@atg.in.gov

ERIC H. WESSAN

Solicitor General

Office of the Iowa Attorney General

1305 E. Walnut Street

Des Moines, Iowa 50319

(515) 823-9117

eric.wessan@ag.iowa.gov

Counsel for the

State of Indiana

Counsel for the

State of Iowa

36

KRIS KOBACH

Attorney General

LIZ MURRILL

Attorney General

DWIGHT CARSWELL

Office of Kansas

Attorney General

120 SW 10th Avenue,

2nd Floor

Topeka, Kansas 66612

(785) 368-8539

dwight.carswell

@ag.ks.gov

J. BENJAMIN AGUIÑAGA

Solicitor General

Office of the Louisiana

Attorney General

1885 North Third Street

Baton Rouge, Louisiana

70802

(225) 485-2458

Aguinagab

@ag.louisiana.gov

Counsel for the

State of Kansas

Counsel for the

State of Louisiana

LYNN FITCH

Attorney General

CATHERINE HANAWAY

Attorney General

SCOTT G. STEWART

Solicitor General

JUSTIN L. MATHENY

LOUIS J. CAPOZZI III

Solicitor General

Office of the Attorney

General

815 Olive Street,

Suite 200

St. Louis, Missouri

63101

(717) 802-2077

Louis.Capozzi

@ago.mo.gov

Acting Solicitor General

Deputy Solicitor General

Mississippi Attorney

General’s Office

P.O. Box 220

Jackson, Mississippi

39205-0220

(601) 359-3680

Scott.Stewart

@ago.ms.gov

Counsel for the

State of Mississippi

Counsel for the

State of Missouri

37

AUSTIN KNUDSEN

Attorney General

MICHAEL T. HILGERS

Attorney General

CHRISTIAN B. CORRIGAN

Solicitor General

Montana Department of

Justice

215 North Sanders

P.O. Box 201401

Helena, Montana

59620-1401

(406) 444-2026

christian.corrigan

@mt.gov

CODY S. BARNETT

Solicitor General

Nebraska Department of

Justice

1445 K Street,

Room 2115

Lincoln, NE 68508

(402) 471-2683

Cody.Barnett

@nebraska.gov

Counsel for the

State of Montana

Counsel for the

State of Nebraska

DREW WRIGLEY

Attorney General

D. ANDREW WILSON

Attorney General

PHILIP AXT

Solicitor General

North Dakota Attorney

General’s Office

600 East Boulevard

Avenue, Dept. 125

Bismarck, North

Dakota 58505

(701) 328-2210

pjaxt@nd.gov

MATHURA SRIDHARAN

Solicitor General

Ohio Attorney General’s

Office

30 East Broad Street,

Floor 17

Columbus, Ohio 43215

(614) 466-8980

mathura.sridharan

@ohioago.gov

Counsel for the

State of North Dakota

Counsel for the

State of Ohio

38

GENTNER F. DRUMMOND

Attorney General

ALAN WILSON

Attorney General

GARRY M. GASKINS, II

Solicitor General

Oklahoma Office of the

Attorney General

313 Northeast

21st Street

Oklahoma City,

Oklahoma 73105

(405) 312-2451

Garry.Gaskins

@oag.ok.gov

THOMAS T. HYDRICK

Solicitor General

JOSEPH D. SPATE

Counsel for the

State of Oklahoma

Counsel for the

State of South Carolina

MARTY J. JACKLEY

Attorney General

JONATHAN SKRMETTI

Attorney General

PAUL S. SWEDLUND

Solicitor General

South Dakota Attorney

General’s Office

1302 East Highway

1889, Suite 1

Pierre, South Dakota

57501

(605) 773-3215

Paul.Swedlund

@state.sd.us

MADELINE CLARK

Solicitor General

Office of the Tennessee

Attorney General and

Reporter

P.O. Box 20207

Nashville, Tennessee

37202-0207

(615) 253-0144

Madeline.Clark

@ag.tn.gov

Counsel for the

State of South Dakota

Counsel for the

State of Tennessee

Deputy Solicitor General

Office of the South

Carolina Attorney General

1000 Assembly Street

Columbia, South

Carolina 29201

(803) 734-3371

josephspate@scag.gov

39

DEREK BROWN

Attorney General

KEITH G. KAUTZ

Attorney General

STANFORD E. PURSER

Solicitor General

Office of the Utah

Attorney General

160 E. 33 S., 5th Floor

Salt Lake City, Utah

84111

(385) 382-4334

spurser@agutah.gov

D. DAVID DEWALD

Deputy Attorney General

Wyoming Attorney

General’s Office Water &

Natural Resources

Division

109 State Capitol

Cheyenne, Wyoming

82002

(307) 777-7895

david.dewald@wyo.gov

Counsel for the

State of Utah

KEN PAXTON

Attorney General

BRENT WEBSTER

First Assistant

Attorney General

AUSTIN KINGHORN

Deputy Attorney

General for Civil

Litigation

KELLIE E. BILLINGS-RAY

Chief, Environmental

Protection Division

Counsel for the

State of Wyoming

CLAYTON SMITH

Assistant Attorney General

Office of the Attorney

General of Texas

Environmental

Protection Division

P.O. Box 12548, MC 066

Austin, Texas

78711-2548

(512) 970-9855

clayton.smith@oag.

texas.gov

Counsel for State of

Texas and Texas Commission on Environmental Quality

40