The U.S. Court of Appeals for the D.C. Circuit has reinstated the “emergency” affirmative defense under Title V of the Clean Air Act, reversing the Environmental Protection Agency’s (“EPA”) 2023 decision to remove it. For more than three decades, 40 C.F.R. § 70.6(g) allowed permit holders to assert a complete defense against liability when excess emissions occurred due to sudden, unforeseeable emergencies beyond the source’s control, provided the facility was properly operated and reasonable steps were taken to minimize the event. In July 2023, EPA eliminated the provision, claiming that it interfered with judicial discretion in assessing penalties and undermined the requirement that emission limits be “continuous.” The D.C. Circuit disagreed, holding in SSM Litig. Grp. v. Env’t Prot. Agency, No. 23-1267, 2025 WL 2552531, at *6 (D.C. Cir. Sept. 5, 2025) that the agency’s rulemaking was “unreasonable and not in accordance with law.”

In its ruling, the Court emphasized that an affirmative defense addresses whether a violation has occurred in the first place, not whether penalties are appropriate, and thus does not intrude on judicial authority. See Id. at *4. The Court further explained that the defense does not suspend emission limits, which remain continuously enforceable; instead, it provides a narrow shield in circumstances that truly qualify as emergencies. Id. The decision is consistent with recent precedent limiting EPA’s efforts to strip similar defenses from state implementation plans and other Clean Air Act programs. See Id.; Environmental Committee of Florida Electric Power Coordinating Group, Inc. v. EPA, 94 F.4th 77 (D.C. Cir. 2024).

To invoke the reinstated defense, a permittee must demonstrate that the exceedance was caused by a sudden and unforeseeable event beyond its control, that the facility was properly operated at the time, that all reasonable steps were taken to minimize emissions, and that timely notice was provided to the permitting authority, typically within two working days. SSM Litig. Grp. v. Env’t Prot. Agency, 2025 WL 2552531, at *1. Events caused by poor design, inadequate maintenance, operator error, or foreseeable equipment issues do not qualify. See Id. This means facilities in regions vulnerable to severe weather, grid failures, or unexpected equipment malfunctions once again have a path to avoid liability for exceedances that could not reasonably have been prevented.

The decision has important implications for both industry and regulators. Facilities will need to revisit their compliance and incident-response protocols to ensure they can meet the evidentiary burden associated with claiming the defense, including careful documentation and timely reporting. Permitting authorities may also revise their permit templates to reflect the reinstated provision. At the same time, EPA may seek rehearing, pursue further rulemaking with a revised rationale, or petition for Supreme Court review. Until then, the emergency affirmative defense is back in effect, restoring an important compliance safeguard for Title V permit holders navigating unavoidable emission events.