Key D.C. Circuit Decision Revives CAA Emergency Event Affirmative Defense

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 defense at 40 CFR 70.69(g). The Preamble to the regulations noted:

EPA believes that the emergency provision of § 70.6(g) is appropriate in order to provide permitted sources with an affirmative defense where an enforcement action is brought for exceedances of technology-based standards due solely to the unforeseeable failure of technology.

57 Fed Reg. 32279.

The regulations defined an emergency as “any situation arising from sudden and reasonably unforeseeable events beyond the control of the source, including acts of God,” that “causes the source to exceed a technology-based emission limitation under the permit, due to unavoidable increases in emissions attributable to the emergency.” Id. § 70.6(g)(1) (2022). To qualify for the defense, the permittee was required to prove that “[a]n emergency occurred,” that the facility was “being properly operated,” and that the permittee had taken “all reasonable steps” to minimize excess emissions during the emergency. Id. § 70.6(g)(3) (2022). If the defense applied, a permittee would not be found in violation of the CAA for exceeding its emission limitations. Id. § 70.6(g)(2) (2022).

EPA Action to Rescind the Emergency Affirmative Defense

 However, in 2023, EPA rescinded the affirmative defense, concluding that it was unlawful. The EPA cited two grounds for the change. First, EPA asserted that the affirmative defense encroached on the judiciary’s authority under the CAA to determine appropriate civil penalties. See 42 USC 7604(a) (giving the federal district courts the authority to impose appropriate civil penalties). Second, it asserted the defense should be rescinded because it could be construed as an unlawful exemption rendering emissions standards non-continuous, in violation of CAA requirements. See 42 USC 7602(k) (defining “emission limitation” or “emission standard” as a requirement that applies “on a continuous basis.”) The Court found both of these grounds to be legally erroneous, and reversed the EPA’s action in rescinding the affirmative defense as arbitrary and capricious.

Alleged Encroachment on the Role of the Judiciary. With regard to the alleged unlawful encroachment on the judiciary’s role, the Court distinguished the full affirmative defense here from the partial affirmative defense to monetary penalties struck down in NRDC v. EPA, 749 F3d at 1063.   The Court relied on Environmental Committee of Florida Electric Power Coordinating Group, Inc. v. EPA, 94 F.4^th 77 (D.C. Cir. 2024), in distinguishing between a true affirmative dense that operates as a complete defense to liability, and a partial affirmative defense that merely limits the available remedies when a source has been determined to be in violation; the former is permissible, the latter is not. Because the Title V emergency affirmative defense is a complete defense to liability, not a limitation on judicial remedies, the Court found EPA’s assertion that the affirmative defense encroached on the role of the judiciary to be erroneous. The Court upheld the emergency affirmative defense as a complete affirmative defense because it relates to the preceding question of liability, rather than impinging upon the court’s authority to impose appropriate civil penalties once liability has been found.

Alleged Illegal Exemption from Continuous Emissions Limitations. Turning to EPA’s second argument, the Court also rejected the EPA’s assertion that the Title V affirmative defense was an illegal exemption from applicable emissions limitations, since it rendered those limitations not “continuous,”’ in violation of the CAA. The Court acknowledged that in Sierra Club v. EPA, 551 F.3d at 1027 – 1028, it held that the CAA requires emission standards to apply on a continuous basis, and thus a regulation that expressly lifted Section 112 emission standards during startup, shutdown and malfunction was contrary to the CAA. However, it distinguished the emergency affirmative defense from the regulations reviewed in Sierra Club. The Court noted that an affirmative defense allows a defendant to avoid liability, but does not alter the underlying legal requirements. The affirmative defense assumes that the legal standard remains in force, but requires judgment for the defendant, even if the plaintiff proves his case. Because the Title V affirmative defense for emergencies does not lift the applicable regulations under the CAA, the emissions standards still apply on a continuous basis, as required by the CAA. The Court therefore determined that a complete affirmative defense to liability does not render an emission limitation non-continuous under 42 U.S.C. § 7602(k), and concluded that EPA therefore could not justify its rescission of the Title V affirmative defense on the ground that it rendered emission limitations non-continuous.

In conclusion, the Court found that EPA’s reasoning did not support its actions in rescinding the affirmative defense of the emergency event, and it determined that no other independent grounds justifying its actions were provided. The Court therefore reversed the rescission of the affirmative defense, restoring it to full effectiveness. 

The DC Circuit’s decision restores an essential tool for Title V air emissions sources facing emergency technological upsets or outages. How EPA responds to the Court’s decision remains to be seen. EPA could choose to appeal the decision or initiate a rulemaking process by re-crafting the rule in a form that complies with the DC Circuit’s decision.

At Dickinson Wright, we will continue to monitor this case and any related regulatory actions by EPA concerning the emergency event affirmative defense under Title V of the CAA. Please reach out to the members of Dickinson Wright’s Environmental, Energy & Sustainability Group with any questions you may have concerning your facility air permits.