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 »

Share | Email| Comments|  Topics: Agency Action, Air, Chevron Deference, Clean Air Act, Emissions, EPA, Hazardous Air Pollutants, Loper Bright, Michigan, Sixth Circuit

On June 18, 2025, the Supreme Court decided EPA v Calumet Shreveport Refining, LLC et al., and its companion case Oklahoma et al. v. EPA, clarifying the tripartite framework for determining venue in Clean Air Act (“CAA” or “Act”) litigation.  Looking at the CAA's venue provision (42 U.S.C. 7607(b)(1)), the Court explained that if a challenge is to an “nationally applicable” EPA action the challenge should be directed to the U.S. Circuit Court of Appeals for the D.C. Circuit and the matter ends there.  But, if the challenge is to a “locally or regionally applicable” EPA action, then typically those challenges belong in the relevant regional Circuit Court.  However, when a “locally or regionally applicable” action falls within the “nationwide scope or effect” exception, which requires the action be (1) “based on a determination of nationwide scope or effect” and (2) accompanied by an EPA finding to the same effect, the Court instructed that the matter should be routed back to the D.C. Circuit.  Applying this understanding of CAA's venue provision, the Court reached different conclusions in Calumet and Oklahoma, finding respectively that the “nationwide scope or effect” exception applied in one instance and not in the other. Read More »

Share | Email| Comments|  Topics: Agency Action, Air, Clean Air Act, D.C. Circuit, EPA, Federal Procedure, Procedure, Refinery, Renewable Fuel Standard, State Implementation Plans, Supreme Court, United States Supreme Court, Venue

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 »

Share | Email| Comments|  Topics: Agency Action, Air, California, Clean Air Act, Climate Change, D.C. Circuit, Emissions, EPA, Federal Procedure, Greenhouse Gas, Legislation, Oil and Gas, Standing, Supreme Court, United States Supreme Court

In March 2024, the County of Bucks filed a controversial suit under state law against a number of large oil companies alleging the County was injured because of the companies’ deceptive conduct with respect to their impact on climate change. The Defendants filed various preliminary objections including lack of subject-matter jurisdiction, arguing that despite the County’s effort to focus the complaint on fraudulent practices, the case at bottom alleged harm from severe weather allegedly due to air emissions, which are governed exclusively by federal law. On May 16, 2025, the Bucks County Court of Common Pleas issued an opinion agreeing with the Defendants and dismissing the case entirely.  See Bucks County v. BP P.L.C., et al., No. 2024-01836 (Bucks Cty. Com. Pl. May 16, 2025). Read More »

Share | Email| Comments|  Topics: Clean Air Act, Climate Change, Pennsylvania, Preemption, Standing

In a decision on February 5, 2025, the Superior Court of New Jersey dismissed the Attorney General of New Jersey’s state tort claims against various energy companies seeking redress for the effects of climate change in Platkin v. Exxon Mobil Corp (N.J. Super. No. MER-L-001797-22).  Because the dispute concerned interstate and global air emissions, which implicate uniquely federal interests, the court concluded that the federal Constitutional structure requires that federal common law preempts these climate-change related tort claims.   Read More »

Share | Email| Comments|  Topics: Air, Clean Air Act, Climate Change, Energy, New Jersey, NJDEP, Toxic Torts

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 »

Share | Email| Comments|  Topics: Air, Clean Air Act, Connecticut, Emissions, Massachusetts, Nuisance, Odors, Pollutants

In an opinion published on December 18, 2024, the Montana Supreme Court found that a provision in the Montana Constitution providing for the right to a “clean and healthful environment” guarantees the right to a stable climate system.  In Held v. State of Montana, 2024 MT 312 (Mont. 2024), the Montana Supreme Court affirmed a trial court decision striking down state law provisions that barred state agencies from considering greenhouse gas (“GHG”) emissions in permitting decisions, finding the law violates the environmental rights guaranteed by the Montana Constitution. Read More »

Share | Email| Comments|  Topics: Air, Citizens Suit, Clean Air Act, Climate Change, Greenhouse Gas, Montana