The U.S. Court of Appeals for the Tenth Circuit issued a decision on August 3, 2026, which clarified the scope of the diligent prosecution bar to citizen suits under the Clean Air Act (“CAA”).  The decision was a partial victory for the environmental organizations that brought the lawsuit and adds to the body of appellate decisions aiming to elucidate this heavily litigated area of the law. Read More »

Share | Email| Comments|  Topics: Air, CERCLA, Citizen Suit, Citizens Suit, Clean Air Act, Colorado, Consent Decree, Diligent Prosecution, Emissions, EPA, Loper Bright, Pollutants, Superfund, Tenth Circuit

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. Read More »

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In June 2026, the United States District Court for the District of New Jersey (the “District Court”) found a Montclair, New Jersey ordinance prohibiting the use of gas-powered leaf blowers to be a valid exercise of state police power not preempted under the federal Clean Air Act (“CAA”). Read More »

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In a recent decision by the United States Court of Appeals for the Sixth Circuit, Sierra Club v. EPA, Nos. 23-3581/3583 (6th Cir. Dec. 5, 2025), the Court invoked its statutory interpretation authority to hold that EPA contravened the plain language of the Clean Air Act (“CAA”) by redesignating the Detroit area as in attainment with the 2015 ozone National Ambient Air Quality Standards (“NAAQS”). Conversely, the Court deferred to EPA’s technical expertise in determining that certain air emissions should be excluded from consideration of the Detroit area’s compliance with the ozone NAAQS because of their qualification as “exceptional events” under the CAA, demonstrating that Courts will continue to defer to agencies’ expertise, but will not defer to agency interpretations of their enabling statutes. Read More »

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On June 20, 2025, the Supreme Court issued it opinion in Diamond Alternative Energy v. EPA, holding fuel producers had standing—and had specifically demonstrated redressability—to challenge California-specific regulations EPA approved under the Clean Air Act.  The Court’s opinion  reversing and remanding to the D.C. Circuit left the merits of the case for another day, but acknowledged that the regulations at issue may be rescinded shortly, mooting most, if not all, of the parties’ controversy. Read More »

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In Conservation Law Foundation, Inc. v. Academy Express, LLC, the Conservation Law Foundation brought a private right of action under the Clean Air Act, alleging that Academy Express, LLC, a bus company, allowed its vehicles to sit idle for excessive periods of time across Massachusetts and Connecticut. No. 20-10032-WGY (D. Mass. 2023). On appeal, the First Circuit decided an interesting question regarding standing: whether smelling odor from vehicle fumes was sufficient to confer standing to sue a particular bus company. The First Circuit said it was and so allowed the case to proceed. Read More »

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In the wake of the Supreme Court’s decision in Loper Bright Enters. v. Raimondo, 244 S.Ct. 2244 (2024), the general breadth and scope of agency decision-making has been called into question. In its recent decision, Huntsman Petrochemical LLC v. EPA, No. 23-1045, 2024 WL 3763355 (D.C. Cir. Aug. 13, 2024), the D.C. Circuit has made it clear that where statutory interpretation is not implicated, the Court will continue to afford EPA’s conclusions involving technical expertise a significant degree of deference. While neither the parties nor the Court attempted to address or reference Loper Bright, the Court articulated a clear standard applicable to agency actions involving statistical and modeling analyses: the Court will examine each step of an agency’s analysis to satisfy themselves that the agency has not “departed from a rational course.” Only where a statistical model “bears no rational relationship to the characteristics of data to which it was applied” will agency action be deemed arbitrary and capricious. Accordingly, regulated entities should be aware that the concept of deference lives on when challenging agency decision-making, even in the wake of the fall of Chevron Deference. Read More »

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On September 14, 2023, in Conservation Law Foundation v. Academy Bus, a Massachusetts District Court held that the members of the Conservation Law Foundation (the “Foundation”) lacked standing to challenge the idling of buses under the Clean Air Act (“CAA”).  Conservation Law Found. v. Acad. Express, LLC., No. 20-10032-WGY, 2023 WL 5984517, at *1 (D. Mass. Sept. 14, 2023). Specifically, the court held that simply breathing in polluted air, without any concrete injury that is fairly traceable to the defendant, is not sufficient to prove an actual injury under the CAA. Read More »

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This post was authored by Trang Do, a summer associate.

In West Virginia v. EPA, the Supreme Court limited the authority of the United States Environmental Protection Agency (EPA) to reduce greenhouse gases by setting emission guidelines for existing power plants, characterizing the energy generation shifting strategy proposed in the Clean Power Plan (CPP) as an overreach of the agency’s power. In a 6-3 decision, with the three liberal justices dissenting, the Court held that the authority to adopt a regulatory program that would significantly alter how the nation’s energy is generated fell under an “extraordinary case” of the major questions doctrine. West Virginia v. EPA 597 U. S. ____ (2022). The major questions doctrine requires that a federal agency have “clear congressional authorization” when acting on issues of great “economic and political significance.” Id. (citing Utility Air Regulatory Group v. EPA, 573 U. S. 302, 324). Read More »

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This Blog Post was authored by Brielle Brown, a summer associate.  Originally published on July 7, 2021, it has been updated to reflect that after a rehearing, the decision was affirmed on July 20, 2021.

A three-judge panel of the Third Circuit held on June 21, 2021, that air emission exceedances governed by a state air permit and duly reported to state or local authorities pursuant to the permit need not be reported again to the United States Environmental Protection Agency (“EPA”) pursuant to the Section 103 reporting requirements of the federal Comprehensive Environmental Response, Compensation, and Liability Act (“CERCLA”). Clean Air Council v. U.S. Steel Corp., 2 F.4^th 112 (3d Cir. 2021); 42 U.S.C. § 9603. The decision was reheard and affirmed on July 20, 2021. Clean Air Council v. U.S. Steel Corp., No. 20-2215, -- F.4^th --, 2021 WL 3045927 (3d Cir., July 20, 2021). The court’s reasoning came down to an interpretation of CERCLA that the phrase “subject to” was intended to mean “governed or affected by” rather than “obedient to.” Id. at *3–4. Thus, air emissions that violate relevant Clean Air Act permits are nevertheless “subject to” that permit and therefore exempt from CERCLA’s reporting requirement. Id. Read More »

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