D.C. Circuit Restores Emergency Affirmative Defense for Title V Permit Holders

On September 5, 2025, the D.C. Circuit reversed the U.S. Environmental Protection Agency’s (EPA) 2023 rescission of the emergency affirmative defense under the Clean Air Act (CAA) for stationary sources that exceed emissions limitations. The ruling in SSM Litigation Group v. EPA, No. 23-1267 (D.C. Cir. Sept. 5, 2025) restores a long-recognized shield against penalties for excess emissions during emergencies, with important implications for Title V permit holders.

The Clean Air Act and EPA Emissions Limitations

Under the CAA, stationary sources are often subject to various technology-based emission standards on certain pollutants and must obtain CAA Title V permits incorporating those emissions limits.[1] A source may be subject to civil penalties and injunctive relief if it exceeds those limits.[2]

Historically, EPA recognized a source could assert an affirmative defense to liability for exceeding an emissions limit if an emergency caused an exceedance of a technology-based limit. EPA had defined an emergency by regulation 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.”[3] This defense shielded a source from enforcement for excess emissions during an emergency, provided the source met the specified regulatory conditions, such as showing the facility was otherwise “being properly operated.”[4]

However, during the final year of the Obama administration, EPA began a rulemaking to rescind the affirmative defense,[5] which the Biden EPA finalized in July 2023.[6]

Challenge to the Defense Recission

An association challenged EPA’s final rule, arguing that EPA did not reasonably explain its decision and failed to act in accordance with the law. A unanimous panel of the D.C. Circuit agreed, rejecting EPA’s two justifications for rescinding the defense.

First, in its 2023 rulemaking, EPA stated that the affirmative defense inappropriately supplanted the Court’s authority to assess penalties for violations of Title V emissions limitations. Citing NRDC v. EPA, 749 F.3d 1055 (D.C. Cir. 2014), EPA had concluded that the affirmative defense was “intrusive on the judiciary’s role” and “limit[ed] a court’s authority or discretion to determine the appropriate remedy in an enforcement action.”[7]

But in 2024, the D.C. Circuit foreclosed this argument in Environmental Committee of Florida Electric Power Coordinating Group, Inc. v. EPA, 94 F.4th 77 (D.C. Cir. 2024). There, the Court distinguished a “complete” defense that wholly removed liability from one that “precludes certain remedies” for a recognized violation, finding that EPA has authority to establish complete defenses through the rulemaking process. Following that reasoning, the D.C. Circuit held the emergency affirmative defense is a complete defense that does not limit judicial remedial powers — and thus is permissible under governing precedent.

Second, EPA had argued the CAA requires emissions limitations to run continuously and that the affirmative defense undermines this requirement. The Court distinguished an affirmative defense that shields against liability for a violation of an emission standard from a regulation that exempts a facility from that emission standard all together. As the Court noted, “[a]n affirmative defense allows a defendant to avoid liability, but it does not alter the underlying legal requirements.”[8] Accordingly, “[b]ecause the emission standards are never lifted, they apply ‘on a continuous basis’ as required by the Clean Air Act.”[9]

Implications for Title V Permit Holders

Concluding that EPA erred in rescinding the affirmative defense, the Court granted the petition and reversed EPA’s recission. Once the mandate issues, EPA’s prior rule allowing the affirmative defense will be restored (note that EPA typically issues a final rule notice to implement a court vacatur). It would seem unlikely that the current administration would seek rehearing or a writ of certiorari. Accordingly:

• For permit holders that still have the affirmative defense listed in their permits, the decision removes any uncertainty as to the legality of raising the defense. While a facility must maintain proper operation in ordinary circumstances, if the facility exceeds a technology-based emission limit under their Title V permit during an “emergency,” the defense will be available as a shield from claims for civil penalties.
• For permit holders that do not have the defense in their permits, sources should consider seeking amendments to include the defense and, at a minimum, address this issue when their permits come up for renewal to ensure the defense is properly referenced.
• Stakeholders should be sure their state regulators align their approved Title V programs with the D.C. Circuit’s ruling. States that already removed the affirmative defense from their program will need to reinstate the defense, while those states that were still in the midst of removing the defense in response to EPA’s 2023 rule should withdraw those proposed changes.

[1] See 42 U.S.C. § 7602(k).

[2] Id. § 7604(a).

[3] 40 C.F.R. § 70.6 (2022).

[4] Id.

[5] See 81 Fed. Reg. 38,645 (June 14, 2016).

[6] See 88 Fed. Reg. 47,029 (Jul. 21, 2023).

[7] 88 Fed. Reg at 47,032.

[8] SSM Litigation Group v. EPA, No. 23-1267 (D.C. Cir. Sept. 5, 2025).

[9] Id. (quoting 42 U.S.C. § 7602(k)).

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