For decades, EPA’s Clean Air Act (CAA) regulations provided an affirmative defense to liability for excess emissions caused by emergency events. In 2023, EPA rescinded the defense.

A coalition of industry groups filed a Petition for Review to the US Court of Appeals for the DC Circuit. The Petition argued that EPA’s rescission relied on erroneous legal justifications. The DC Circuit agreed, granted the Petition, and reversed the rescission.

The Defense and Title V Permits
In 1990, Congress amended the CAA to consolidate air pollution requirements into a single document, the Title V permit. In 1992, EPA promulgated “a narrow defense for stationary sources that exceed their emission limitations due to an emergency event.”

To justify the rescission in 2023, EPA said new legal analysis showed the defense unlawfully restricted the authority of courts to impose CAA penalties. In addition, EPA asserted the defense prevented emission standards from being continuous, as the CAA requires.

Erroneous Legal Justifications
EPA “offered no independent policy rationale.” When an agency action is “premised entirely on erroneous legal justifications, it must be reversed.”

The DC Circuit, relying on a 2024 decision, said EPA had authority to create “a complete affirmative defense, like the one at issue here… because it relates to the antecedent question of liability and therefore does not impinge on the judiciary’s authority” to assess penalties.

In addressing the “continuous standard” issue for the first time, the DC Circuit said, “we now hold that a complete affirmative defense to liability does not render an emission limitation non-continuous.”

To see the opinion https://media.cadc.uscourts.gov/opinions/docs/2025/09/23-1267-2133591.pdf