On January 2, 2026, the D.C. Circuit declined to rehear en banc its prior order restoring the Clean Air Act’s (CAA) Title V affirmative defense to liability for excess emissions caused by emergency events. A group of environmental organizations had petitioned for rehearing en banc, arguing that the court’s reasoning violated D.C. Circuit precedent.

First enacted by Congress in 1990, Title V of the CAA establishes a permitting regime for stationary sources of air pollution, including power plants. Although Title V itself does not establish new emission standards or limitations, it provides a framework for compiling all applicable requirements into a single operating permit, along with all relevant monitoring recordkeeping and reporting requirements. In 1992, the Environmental Protection Agency (EPA) promulgated regulations to implement Title V, and in those regulations created an affirmative defense for stationary sources that exceed their permit emissions limitations due to an emergency event. To claim the defense, operators must show that a qualifying emergency occurred, the facility was being properly operated, and the operator had taken “all reasonable steps” to minimize excess emissions during the emergency.

In 2023, the EPA rescinded the Title V emergency affirmative defense on the ground that it unlawfully encroached on the judiciary’s role to impose “any appropriate civil penalties” for CAA violations, or in the alternative, that the defense was unlawful because it operated as an exemption from otherwise applicable emissions limitations, thus violating the D.C. Circuit’s prior interpretation of the CAA to require emissions standards and limitations to apply continuously. A coalition of trade associations whose members operate stationary sources of air pollution petitioned the D.C. Circuit for review of EPA’s rescission.

On September 5, 2025, the D.C. Circuit held that the EPA’s recission of the Title V emergency affirmative defense was not in accordance with law. The court explained that the defense does not “preclude[] certain remedies after a source has violated an emission rule,” which would be an improper limitation on remedies. Rather, the defense serves as a complete defense to CAA liability, so it is “permissible because it relates to the antecedent question of liability and therefore does not impinge on the judiciary’s authority to award ‘appropriate civil penalties.’” The court also explained that the defense did not render emissions limitations non-continuous because the defense does not lift or suspend applicable standards—the limitations still apply, even when exceeded, but the affirmative defense merely eliminates any liability for exceedances caused by an emergency beyond the control of the facility. The D.C. Circuit’s opinion builds on and clarifies its prior holding in Florida Electric Power Coordinating Group v. EPA, which permitted complete affirmative defenses to start up, shut down, and malfunction exemptions from CAA state implementation plans.

A group of environmental organizations petitioned for rehearing of the order, arguing that D.C. Circuit’s reasoning violated its own precedent regarding the continuity of emissions limitations. The D.C. Circuit declined to rehear the case en banc.

The D.C. Circuit’s January 2, 2026, order denying rehearing en banc can be accessed here, and its September 5, 2025, order can be accessed here. Both were issued in Case No. 23-1267.