On September 5, 2025, the DC Circuit issued its opinion in SSM Litigation Group v. EPA , reversing EPA’s rescission of the longstanding emergency event affirmative defense under Title V of the Clean Air Act (“CAA”). The Court’s decision restores an important tool for all Title V sources facing potential enforcement as a result of emergency technological upsets or outages.

In examining the affirmative defense, the Court noted that for decades, EPA had recognized the reality that emergencies and other unforeseen events may cause a stationary source of air pollution to exceed its permitted emission limitations. This reality was reflected in EPA’s July 21, 1992, initial adoption of the Part 70 regulations implementing the provisions of Title V, which included the emergency affirmative defen

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