In a significant decision for Clean Air Act enforcement, the U.S. District Court for the Eastern District of California held that citizens may pursue Clean Air Act claims against a state or local air agency in their regulatory capacity for allegedly failing to carry out State Implementation Plan (SIP) obligations.

In Central Valley Air Quality Coalition v. San Joaquin Valley Unified Air Pollution Control District, No. 1:23-cv-00794 (E.D. Cal. July 16, 2026), the court denied the San Joaquin Valley Air District's (the “Air District”) motion to dismiss, concluding that Ninth Circuit precedent permits citizen suits against government regulators when they allegedly violate enforceable SIP requirements.

Several environmental justice organizations brought suit pursuant to the Clean Air Act’s citizen suit provision, which provides that "any person may commence a civil action on his own behalf . . . against any person (including (i) the United States, and (ii) any other governmental instrumentality or agency to the extent permitted by the Eleventh Amendment to the Constitution) who is alleged to have violated (if there is evidence that the alleged violation has been repeated) or to be in violation of (A) an emission standard or limitation under this chapter or (B) an order issued by the Administrator or a State with respect to such a standard or limitation[.]"  42 U.S.C. § 7604(a)(1); CAA § 304(a)(1).

The plaintiffs alleged that the Air District failed to properly implement California's SIP by administering its New Source Review (NSR) offset program in a manner inconsistent with Clean Air Act requirements.  Among other allegations, the complaint asserted that the Air District failed to require the appropriate emissions offset ratio after the San Joaquin Valley was reclassified as an extreme ozone nonattainment area; the Air District improperly credited emissions reductions that were not legally surplus; and these practices resulted in violations of SIP requirements governing emissions offsets and California's Annual Offset Equivalency Tracking System.

Rather than addressing the merits, the Air District argued that the Clean Air Act's citizen suit provision does not authorize lawsuits against regulatory agencies acting in their regulatory capacity.  The Air District argued that the citizen suit provision was appropriately geared toward regulated facilities, citing to the Sixth Circuit decision in Sierra Club v. Korleski, wherein the court concluded that the Clean Air Act does not authorize citizen suits against state regulators for failing to regulate. 

The district court rejected the Air District's argument, finding that it was bound by Ninth Circuit precedent, including Comm. for a Better Arvin v. EPA, 786 F.3d 1169 (9th Cir. 2015) and Association of Irritated Residents v. EPA, 10 F.4th 937 (9th Cir. 2021) (“AIR”).  In both cases, the Ninth Circuit recognized that certain SIP commitments requiring governmental action are enforceable through the Clean Air Act's citizen suit provision.  More specifically, the court noted that in Arvin, the Ninth Circuit found that “California’s commitment to propose and adopt emission control measures and to achieve aggregate emission reductions . . . are enforceable emission standards or limitations,” and thus, the use of the citizen’s suit provision was appropriate.  Similarly, the court noted that in AIR, the Ninth Circuit held that citizens could utilize Section 304(a)(1) to challenge an air district’s failure to enforce the EPA-approved Enhanced Enforcement Activities Program on the basis that it “created an additional emissions limitation.”  Thus, in reliance on both decisions, the court concluded that enforceable SIP provisions amount to emission standards of limitations under Section 304(a)(1).

The court's ruling addressed only whether the plaintiffs may proceed with their lawsuit. The plaintiffs must still prove that the Air District actually violated enforceable SIP obligations and that those obligations qualify as “emission standards or limitations” under the Clean Air Act. Nonetheless, the holding expands the litigation risks faced by air agencies within the Ninth Circuit.  Historically, most Clean Air Act citizen suits target industrial facilities alleged to be violating permits or emission limitations.  This decision provides that, at least in the Ninth Circuit, governmental agencies themselves may also face citizen suits when plaintiffs allege that the agencies failed to carry out mandatory SIP obligations.

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