Pittsburgh, PA and Washington, DC
Environmental Alert
(by Joseph Schaeffer, Gina Buchman and Ryan McCann)
On September 5, 2025, the United States Court of Appeals for the District of Columbia Circuit (D.C. Circuit) reinstated an affirmative defense under the Clean Air Act (CAA) for exceedances occurring as a result of an emergency, ruling that the Environmental Protection Agency’s (EPA) rescission of that defense was arbitrary and capricious. EPA had first established that affirmative defense for state-issued Title V permits in 1992, 57 Fed. Reg. 32250, 32306, and then expanded it to federally-issued Title V permits in 1996, 61 Fed. Reg. 34202, 34239. In doing so, it created a limited shield to liability for exceedances of emissions limitations if the operator could prove that the exceedance was due to “any situation arising from sudden and reasonably unforeseeable events beyond the control of the source, including acts of God ….” 40 C.F.R. § 70.6(g)(2). By 2016, however, EPA had concluded that the affirmative defense unlawfully encroached on the judiciary’s role to impose appropriate civil penalties for CAA violations or, alternatively, rendered applicable emissions limitations “non-continuous” in violation of 42 U.S.C. § 7602(k). EPA then rescinded the regulation affording the affirmative defense in 2023. 88 Fed. Reg. 47029, 47030–31
SSM Litigation Group (SSM), a coalition of interest groups representing Title V permit holders, petitioned the D.C. Circuit for review. After first disposing of EPA’s challenge to SSM’s standing, the Court turned to whether EPA’s elimination of the affirmative defense was arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.
EPA’s merits-based argument was two-pronged. The CAA allows any person to commence a civil action against another person or entity who is alleged to have violated an emission standard or limitation. …