On Sept. 5, 2025, the D.C. Circuit reversed EPA’s 2023 rule rescinding the “startup, shutdown and malfunction” (SSM) affirmative defense under the Title V permitting program. See SSM Litigation Group v. EPA, Case No. 23-1267 (D.C. Cir. Sept. 5, 2025). The decision carries implications for Title V programs nationwide and for stationary source regulations more broadly.
Why Did EPA Remove the Emergency Affirmative Defense Under Title V in 2023?
In 2023, the EPA issued a rule removing emergency affirmative defenses from Title V operating programs. 88 Fed. Reg. 47029 (Jul. 21, 2023). EPA promulgated this rule following two D.C. Circuit opinions, NRDC v. EPA (2024) and U.S. Sugar Corp. v. EPA (2016), which found that SSM affirmative defense provisions under Title V constituted “an impermissible intrusion on the judiciary’s role.” Id. The 2023 rule removed the “emergency” affirmative defense under 40 C.F.R. §§ 70.6(g) and 71.6(g) because, according to EPA, these provisions were inconsistent with Clean Air Act (CAA) enforcement and the court’s decision in NRDC. As a result of the 2023 rule, any state implementation plan (SIP) that included affirmative defenses needed to be revised and re-submitted to the Agency for review and approval.
In 2024, however, the D.C. Circuit distinguished between two different types of affirmative defenses: a complete defense for emergency situations and a defense limiting remedies after a violation has occurred. Environ. Comm. Fl. Elec. Power v. EPA, 94 F.4th 77, 114 (D.C. Cir. 2024) (Florida Electric). Following the Florida Electric decision, EPA issued a memorandum discussing how the Agency intended to address SIP provisions that various states submitted in the wake of the prior D.C. Circuit cases.
The D.C. Circuit’s Holding Reversing EPA’s 2023 Rule
The recent SSM decision clarified NRDC, holding that only the latter defense (limiting remedies) intrudes on the judiciary’s ability to assess civil penalties, while complete affirmative defenses—such as those previously available in Title V’s emergency affirmative defense provisions—are permissible. SSM, at *10. Fundamentally, complete affirmative defenses pertain to the question of liability, which the court held is a threshold question determined before the judiciary awards appropriate civil penalties for CAA violations. Id. The court found EPA’s interpretation that a Title V complete affirmative defense that unlawfully encroached on the judiciary’s role was too broad and was foreclosed by the 2024 Florida Electric decision. SSM, at *11. Accordingly, a complete Title V affirmative defense is permissible under the CAA.
The court also struck down EPA’s second justification for removal of the Title V affirmation defense under the 2023 rule. There, EPA premised the removal, in part, on the grounds that a complete affirmative defense for emission exceedances of limitations set forth in Title V permits would render an emission limitation not “continuous.” SSM, at *12. The court also rejected EPA’s justification, holding that the 2023 rule conflated two legal concepts—an affirmative defense to liability and a retroactive exemption from a permit emission standard. The court held that an affirmative defense relieves a permittee from liability but does not change the underlying legal standard (i.e., the requirement that an emission limitation be continuous). Id.
Implications for Industry with the Emergency Affirmative Defense’s Restoration
There are numerous potential EPA regulatory actions that may follow the court’s decision in SSM. Most notably, it is now clear that Title V emergency affirmative defense provisions that provide a complete defense to liability are permissible. In June 2024, EPA proposed removing affirmative defense provisions in 18 source sector rules under CAA sections 111 or 112, and in August 2025, finalized removing the affirmative defense provisions for one sector, polyether polyols production. In October 2024, EPA also finalized removing affirmative defense provisions to civil penalties arising from violations caused by malfunctions for the oil and gas sector under New Emission Standards for Hazardous Air Pollutant (NESHAP) regulations at 40 C.F.R. Part 63, subparts HH and HHH. Following the SSM decision, EPA may amend these and other regulations the Agency deems necessary or appropriate to retain considering the court’s decision. In the near term, Title V permittees may consider modifying permits to add emergency affirmative defense provisions. Owners or operators of sources with Title V permits that include an emergency provision may seek to raise it as a defense to liability if an emission limit exceedance arises from an emergency. More broadly, industries across sectors should closely monitor EPA’s potential regulatory responses to the SSM decision.