On May 28, 2026, the U.S. Environmental Protection Agency (EPA) issued a final rule reinstating the longstanding emergency affirmative defense provision under the Clean Air Act’s Title V operating permit programs (the “Emergency AD” rule).
The rule restores the regulatory text at 40 C.F.R. § 70.6(g), governing state operating permit programs, and its parallel provision at 40 C.F.R. § 71.6(g), governing the federal operating permit program, to their form before EPA’s rescission in a July 2023 rulemaking (88 FR 47029).
EPA’s action implements the mandate of the D.C. Circuit’s September 5, 2025 decision in SSM Litigation Group v. EPA, which invalidated the 2023 rule as resting on erroneous legal justifications.
The reinstated provision affords permit holders an affirmative defense to enforcement actions for noncompliance with technology-based emission limitations when the noncompliance results from an “emergency,” defined as a sudden and reasonably unforeseeable event beyond the source’s control, including acts of God, that requires immediate corrective action and causes unavoidable emissions increases. Notably, the rule does not revise the prior regulatory language but simply reinstates the defense as it previously existed, and it is limited to the Title V emergency affirmative defense, leaving separate startup, shutdown, and malfunction (SSM) matters unaddressed. As a result, sources operating under Title V permits once again have the emergency affirmative defense available in enforcement proceedings involving qualifying emergency conditions.
The reinstatement of the Title V emergency affirmative defense restores a compliance mechanism that many regulated facilities had relied upon directly or indirectly before EPA’s 2023 rulemaking.
For Title V sources in Puerto Rico, however, it remains to be seen how the reinstated rule will be reflected in existing, new or renewed operating permits and implemented by the Puerto Rico Department of Natural and Environmental Resources (DNER) and EPA Region 2. Regulated entities should continue to maintain thorough records of emergency events and their response efforts and monitor future permitting and regulatory developments that may affect the availability and application of the defense.
For more information regarding this rule or its potential implications for your operations, please contact a member of our Environmental practice team.
