NOT FOR PUBLICATION FILED

UNITED STATES COURT OF APPEALS FEB 24 2026

MOLLY C. DWYER, CLERK

U.S. COURT OF APPEALS

FOR THE NINTH CIRCUIT

LITTLE MANILA RISING, a nonprofit No. 24-6990 corporation; MEDICAL ADVOCATES Agency Nos. EPA–R09–OAR– FOR HEALTHY AIR, a nonprofit 2024–0250 corporation; SIERRA CLUB, a nonprofit EPA–R09– OAR–2024–0301 corporation, Environmental Protection Agency Petitioners, MEMORANDUM*

v.

UNITED STATES ENVIRONMENTAL

PROTECTION AGENCY; MICHAEL

REGAN, in his official capacity as Administrator of the U.S. Environmental Protection Agency; MARTHA GUZMAN ACEVES, Regional Administrator of Region 9 of U.S., in her official capacity as Regional Administrator for Region IX of the U.S. Environmental Protection Agency,

Respondents,

----------------------------------------

SAN JOAQUIN VALLEY UNIFIED AIR

POLLUTION CONTROL DISTRICT,

Intervenor.

* This disposition is not appropriate for publication and is not precedent except as provided by Ninth Circuit Rule 36-3. On Petition for Review of an Order of the Environmental Protection Agency

Argued and Submitted November 19, 2025 San Francisco, California

Before: S.R. THOMAS, BRESS, and MENDOZA, Circuit Judges. Dissent by Judge BRESS. Various environmental groups (“petitioners”) challenge the EPA’s final rule

granting California a one-year extension for the San Joaquin Valley’s “five percent

plan,” 42 U.S.C. § 7513a(d), to attain the 1997 annual National Ambient Air Quality

Standard (NAAQS) for fine particulate matter with an aerodynamic diameter of less

than or equal to 2.5 micrometers (PM2.5). See 89 Fed. Reg. 91263, 91263–69 (Nov.

19, 2024). We have jurisdiction under 42 U.S.C. § 7607(b)(1). We review “legal

questions, including questions of statutory interpretation, de novo,” without

deference to prior agency interpretations. Lopez v. Garland, 116 F.4th 1032, 1036

(9th Cir. 2024) (discussing Loper Bright Enters. v. Raimondo, 603 U.S. 369, 394

(2024)). The Administrative Procedure Act requires courts to “hold unlawful and

set aside agency action” that is “arbitrary, capricious, an abuse of discretion, or

otherwise not in accordance with law.” 5 U.S.C. § 706(2)(A).

We assume the parties’ familiarity with the facts and regulatory framework.

We conclude that EPA’s extension was permitted under the Clean Air Act (CAA),

but that an EPA regulation, 40 C.F.R. § 51.1005(c), nonetheless prohibited the

extension. We thus grant the petition and remand to EPA without vacatur.

2 24-6990 I

EPA had statutory authority to grant its one-year extension. Specifically,

Subpart 1 of the CAA, 42 U.S.C. § 7502(a)(2)(C), (D), permits EPA’s extension of

the attainment date for a section 189(d) five percent plan when, as here, the State has

complied with the designated statutory criteria.

In Association of Irritated Residents v. EPA, 423 F.3d 989, 994–95 (9th Cir.

2005) (AIR), we addressed whether EPA could rely on Subpart 1’s general

provisions, see 42 U.S.C. § 7502, to set the initial attainment date for a section

189(d) five percent plan, 42 U.S.C. § 7513a(d), for PM-10. 1 The problem we

confronted in AIR was that Subpart 4 did not itself provide an attainment date for a

section 189(d) five percent plan. AIR, 423 F.3d at 993. In arguing that EPA could

not utilize Subpart 1, the petitioners relied on Subpart 4’s attainment date rules in

§ 7513(e), which enables a five-year extension of the PM-10 deadline before a non-

attainment determination––thereafter triggering § 189(d) and the requirement of five

percent annual reductions in PM-10. Id. at 994–95. The petitioners contended that

the Subpart 4 attainment date rules in § 7513(e) were “exclusive,” which would

therefore “leave the EPA with no ability to set a new date at all once a PM-10 area

has missed its deadline.” Id.

1 While Subpart 4 addresses PM-10, a different pollutant, courts have interpreted this subpart to cover PM2.5. See NRDC v. EPA, 706 F.3d 428, 436 (D.C. Cir. 2013).

3 24-6990 We rejected petitioners’ position, holding that EPA could utilize the general

provisions in Subpart 1 to provide the attainment date for a section 189(d) five

percent plan. Id. at 994–95. We explained that “there are essentially two statutory

pathways through which PM-10 attainment deadlines may be changed”––those

found in the generally applicable Subpart 1 provisions, see 42 U.S.C. § 7502, and

those set forth in PM-specific Subpart 4, see 42 U.S.C. §§ 7513, 7513a. Id. at 993.

We reasoned that because “[n]o language in Subpart 4 prohibits the EPA’s

application of the general provisions to change attainment deadlines,” “the statutory

scheme authorizes the EPA to look to [§ 7509(d) in Subpart 1] in order to set a new

attainment deadline once the EPA has determined that a PM-10 area has failed to

attain the standard.” Id. at 994–95. We concluded that EPA’s interpretation,

“looking to the general provisions to provide an alternative path for setting a new

PM-10 attainment deadline, is the correct interpretation of the statutory provisions

that, when viewed in the full statutory context, are not ambiguous.” Id. at 995.

Under the logic of AIR, because Subpart 4 does not set attainment dates or

extensions for five percent plans, Subpart 1’s generally applicable provisions furnish

the basis for both attainment dates and extensions, including the one-year extension

in 42 U.S.C. § 7502(a)(2)(C). Just as “[n]o language in Subpart 4 prohibits the

EPA’s application of the general provisions to change attainment deadlines,” AIR,

423 F.3d at 994, no language in Subpart 4 prohibits the Subpart 1 general extension

4 24-6990 periods from applying to five percent plan attainment deadlines. See also 42 U.S.C.

§ 7502(a)(2)(D) (“This paragraph shall not apply with respect to nonattainment areas

for which attainment dates are specifically provided under other provisions of this

part.” (emphasis added)). So EPA’s one-year extension of the five percent plan

attainment date was permitted under § 7502(a)(2)(C).

II

Despite the CAA authorizing EPA’s one-year extension, EPA’s PM2.5 SIP

Requirements Rule, 40 C.F.R. § 51.1005(c), unambiguously prohibits the extension.

Starting with the text, § 51.1005(c) provides that “[i]f a Serious area fails to attain a

particular PM2.5 NAAQS by the applicable Serious area attainment date, the area is

then subject to the requirements of section 189(d) of the Act, and, for this reason,

the state is prohibited from requesting an extension of the applicable Serious area

attainment date for such area.” The parties do not dispute that the San Joaquin

Valley “fail[ed] to attain [the] particular PM2.5 NAAQS by the applicable Serious

area attainment date” of December 31, 2023. Nor do the parties dispute that the San

Joaquin Valley is subject to § 189(d) of the CAA with regards to PM2.5. The plain

text of the regulation therefore clearly prohibits EPA from granting an extension of

the attainment date for a section 189(d) five percent plan.

The CAA’s statutory structure, our decision in AIR, and the Rule’s history

cannot change this result because interpreting a regulation “begins with the . . . text,

5 24-6990 and ends there as well if the text is unambiguous.” Mission Hen, LLC v. Lee, 137

F.4th 1008, 1014 (9th Cir. 2025) (quoting BedRoc Ltd., LLC v. United States, 541

U.S. 176, 183 (2004)); see also League of Cal. Cities v. FCC, 118 F.4th 995, 1015

(9th Cir. 2024) (“Regulations are interpreted according to the same rules as

statutes[.]” (citation modified)). Moreover, we do not defer to the agency’s

interpretation where, as is the case here, the regulation is unambiguous. See Kisor

v. Wilkie, 588 U.S. 558, 574 (2019) (“[A] court should not afford . . . deference [to

an agency’s interpretation of a regulation] unless . . . the regulation is genuinely

ambiguous.”).

Because EPA’s extension is prohibited under the agency’s regulations, we

grant the petition for review. However, we recognize the ongoing regulatory efforts

concerning the NAAQS attainment in the San Joaquin Valley. See, e.g., 90 Fed.

Reg. 31906 (July 16, 2025) (proposed attainment finding for the San Joaquin Valley

area for the PM2.5 standard by the December 2024 extended attainment date based

on air quality monitoring from 2022 through 2024). Under these circumstances, we

remand the extension action to EPA without vacatur, to permit further agency action

consistent with this decision. See Cal. Cmtys. Against Toxics v. EPA, 688 F.3d 989,

992 (9th Cir. 2012).

PETITION FOR REVIEW GRANTED; REMANDED.2

2 We decline to award costs of litigation under 42 U.S.C. § 7607(f).

6 24-6990

FILED

FEB 24 2026

Little Manila et al. v. EPA, No. 24-6990

MOLLY C. DWYER, CLERK

BRESS, Circuit Judge, dissenting: U.S. COURT OF APPEALS

I agree that the one-year extension for the San Joaquin Valley section 189(d)

five percent plan was permitted under Subpart 1 of the Clean Air Act (CAA). I

therefore agree with the reasoning in Part I of the court’s disposition. But I disagree

with the majority’s counterintuitive conclusion, set forth in Part II, that the EPA

nonetheless tied its hands in PM2.5 SIP Requirements Rule, 40 C.F.R. § 51.1005(c),

thereby prohibiting through its own regulation Subpart 1 extensions that the statute

allows it to confer.

I appreciate the majority’s focus on the final clause of § 51.1005(c), providing

that once an area is “subject to the requirements of section 189(d) of the Act,” “the

state is prohibited from requesting an extension of the applicable Serious area

attainment date for such area.” Id. That clause, however, must be read in context

and in view of the CAA’s structure as a whole. See, e.g., Kisor v. Wilkie, 588 U.S.

558, 576 (2019); Davis v. Michigan Dep’t of Treasury, 489 U.S. 803, 809 (1989).

Read in that light, § 51.1005(c) does not prohibit extensions under Subpart 1, so I

would deny the petition for review.

Based on Association of Irritated Residents v. EPA, 423 F.3d 989, 994–95 (9th

Cir. 2005) (AIR), when EPA incorporated Subpart 1’s provisions addressing

attainment dates for five percent plans, see 40 C.F.R. § 51.1004(a)(3), it is more

1 reasonable to conclude that EPA also incorporated Subpart 1’s extension provision,

because the extensions work hand in glove with the attainment dates. See, e.g., 42

U.S.C. § 7502(a)(2)(A), (C) (providing attainment dates and extensions for

nonattainment areas in Subpart 1). As EPA explained in granting the November

2024 extension, Subpart 1’s “section [7502] controls for purposes of setting an

attainment date for a plan required under CAA section 189(d) because the provisions

of subpart 4, including section [7513](c), do not specifically provide authority for

establishing attainment dates for 189(d) attainment.” 89 Fed. Reg. 91263, 91266

(Nov. 19, 2024). Therefore, § 51.1005(c) only “prohibits a state subject to section

189(d) from applying for an extension of the applicable attainment date in excess of

that which is permitted for an attainment plan under section 189(d).” Id. That is, an

“area subject to section 189(d) may not apply for an extension of the applicable

attainment date under section [7513](e).” Id.

While EPA perhaps could have been clearer in its regulation, the language in

question in § 51.1005(c), properly understood in context, merely clarifies that a five

percent plan cannot receive the longer extensions in Subpart 4; it does not mean that

the other extensions in Subpart 1 are disallowed. Section 51.1005(c) provides that

the state cannot seek “an extension of the applicable Serious area attainment date

for such area.” 40 C.F.R. § 51.1005(c) (emphasis added). That “applicable” date is

a reference to the date established in Subpart 4, because a serious nonattainment area

2 only becomes “subject to CAA section 189(d),” id., if it fails to meet the Subpart 4

requirements by the required date. The regulation is therefore a prohibition against

further Subpart 4 extensions, not a disallowance of any extensions that Subpart 1

may otherwise allow.

This is supported by EPA’s reasoning when it promulgated the PM2.5 SIP

Requirements Rule. EPA noted then that “neither CAA section 189(d) nor other

sections in subpart 4 explicitly establish or provide the authority to establish a new

attainment date for the area,” so “EPA must look to other provisions of part D of the

CAA to provide authority for a new attainment date,” which are located in Subpart

1, specifically 42 U.S.C. §§ 7502(a)(2) and 7509(d)(3). 81 Fed. Reg. 58010, 58106

(Aug. 24, 2016). EPA thus fairly indicated that all of § 7502(a)(2) would be applied

to section 189(d) five percent plans, which includes the extension provision in

§ 7502(a)(2)(C). See id. (explaining that “the EPA must establish a new attainment

date according to the provisions of CAA section [7509](d)(3) and [7502](a)(2).”).

Rather than blanketly prohibit extensions as the majority suggests, the text of

40 C.F.R. § 51.1005(c) incorporates Subpart 1’s generally applicable extension

provision through its reference to “the requirements of section 189(d) of the Act.”

In light of AIR, being “subject to the requirements of section 189(d) of the Act”

includes being subject to Subpart 1 and 42 U.S.C. § 7502(a)(2). The last sentence

of § 51.1005(c) is therefore better understood to clarify that such areas cannot

3 request extensions under Subpart 4 because only Subpart 1 supplies the attainment

dates and extensions at that point in the compliance process. See 40 C.F.R.

§ 51.1005(c) (once “subject to the requirements of section 189(d) of the Act,” “the

state is prohibited from requesting an extension of the applicable Serious area

attainment date for such area”); see 42 U.S.C. § 7513(e) (only providing extensions

for serious areas before a non-attainment determination).

Common sense and the CAA’s overall structure likewise support EPA’s

interpretation. It is doubtful that EPA would incorporate Subpart 1’s attainment

dates, while simultaneously (and without explanation) prohibiting extensions that

are statutorily associated with the date. As observed earlier, attainment dates and

extensions are often paired throughout the CAA. See, e.g., 42 U.S.C. §§ 7502(a)(2),

7513(c)–(e). If EPA had wanted to affirmatively prohibit extensions that the statute

allows, something in the regulatory history would have made that intent apparent.

In any event, to the extent that the majority’s reading of 40 C.F.R. § 51.1005(c)

is plausible, the regulation is at least “genuinely ambiguous” under Kisor. See Kisor,

588 U.S. at 573. “Kisor instructs that courts owe deference to an agency’s

interpretation of its own rules where (1) the regulation is ‘genuinely ambiguous,’ (2)

the interpretation is ‘reasonable,’ and (3) the interpretation is entitled to ‘controlling

weight.’” United States v. Yafa, 136 F.4th 1194, 1197 (9th Cir. 2025) (quoting Kisor,

588 U.S. at 574–79). For the reasons already articulated—based on text, context,

4 and our prior decision in AIR—§ 51.1005(c) is at minimum genuinely ambiguous on

the question before us. It is not unambiguous in petitioners’ favor. And the agency’s

interpretation is also reasonable, in that it “come[s] within the zone of ambiguity

[we] ha[ve] identified after employing” the standard tools of construction. Kisor,

588 U.S. at 576.

“[T]he character and context of the agency interpretation” would also entitle

it to some weight. Id. “While this inquiry ‘does not reduce to any exhaustive

test,’ Kisor instructs courts to consider whether the interpretation (1) constitutes the

agency’s ‘official position, rather than any more ad hoc statement not reflecting the

agency’s views,’ (2) implicates the agency’s ‘substantive expertise,’ and (3) reflects

the agency’s ‘fair and considered judgment.’” Yafa, 136 F.4th at 1199 (quoting

Kisor, 588 U.S. at 576–79).

In this case, EPA’s interpretation constitutes the agency’s “official position”

because it comes from EPA’s notice and comment rulemaking. See 89 Fed. Reg. at

91266. And it implicates EPA’s substantive expertise because the extension involves

EPA’s statutory authority to set and oversee ambient air quality standards and the

complicated rules for attainment deadlines. Kisor, 588 U.S. at 577–78. Finally,

EPA’s reading reflects its “fair and considered judgment,” id. at 579 (citation

omitted), because EPA’s interpretation is consistent with AIR and EPA’s longstanding

position that five percent plan deadlines are subject to Subpart 1, specifically 42

5 U.S.C. §§ 7502(a)(2) and 7509(d)(3). See 89 Fed. Reg. at 91266 & n.42; 81 Fed.

Reg. at 58106. EPA’s interpretation therefore does not reflect a “‘convenient

litigating position’ or ‘post hoc rationalizatio[n] advanced’ to ‘defend past agency

action against attack.’” Kisor, 588 U.S. at 579 (quoting Christopher v. SmithKline

Beecham Corp., 567 U.S. 142, 155 (2012)).

In sum, 40 C.F.R. § 51.1005(c) does not prohibit an extension that the CAA

allows EPA to confer. I respectfully dissent.

6