Supreme Court Issues Split Rulings on Clean Air Act Venue Disputes

On June 18, 2025, the U.S. Supreme Court issued decisions in two significant Clean Air Act cases — EPA v. Calumet Shreveport Refining and Oklahoma v. EPA — clarifying the appropriate venue for legal challenges to certain final EPA actions. In Calumet, the Court held that EPA’s universal denials of small-refinery-exemption (SRE) petitions under the Renewable Fuel Standard program were “based on a determination of nationwide scope or effect,” and thus challenges may only be brought in the D.C. Circuit Court of Appeals. By contrast, the Court in Oklahoma held that challenges to EPA’s disapproval of State Implementation Plans (SIPs) belong in the applicable regional circuit courts because the agency’s determinations were based on facts and rationales unique to each state. Although some gray areas remain, the twin decisions put several long-standing venue issues to rest and should encourage quicker resolution of Clean Air Act regulatory challenges.

Legal Framework

The Clean Air Act’s venue provision (42 U.S.C. § 7607(b)(1)) distinguishes between “nationally applicable” EPA actions, which are subject to review solely by the D.C. Circuit, and “locally or regionally applicable” actions, which are typically reviewed in regional circuit courts. However, the statute creates an exception: if a locally or regionally applicable action is “based on a determination of nationwide scope or effect” and EPA publishes that determination, venue reverts to the D.C. Circuit. This statutory framework is designed to channel issues of national significance — such as New Source Performance Standards (NSPS) and National Emission Standards for Hazardous Air Pollutants (NESHAPs) — to a centralized forum, while reserving region-specific matters for more local adjudication.

Making matters more complex, EPA sometimes aggregates multiple individual decisions into a single consolidated proceeding in an apparent effort to boost the odds that, collectively, the decisions will be seen as having “nationwide scope or effect.” Circuit splits concerning venue have led to lengthy delays and additional litigation that has distracted from timely resolution of Clean Air Act regulatory challenges.

The Supreme Court’s Decisions

EPA v. Calumet Shreveport Refining: In a 7 – 2 opinion by Justice Thomas, the Supreme Court reversed the Fifth Circuit, holding that although EPA’s omnibus denial of SRE petitions were locally or regionally applicable to individual petroleum refineries, the particular denials before the Court fall within the statutory exception due to the agency’s reliance on legal and economic rationales of “nationwide scope or effect.” In issuing the denials, EPA had relied on a “Renewable Identification Number (RIN) passthrough” theory to conclude the refineries did not face “disproportionate economic hardship.” The Court emphasized that EPA had adopted this legal and economic determination to presumptively resolve all SRE petitions. Refinery-specific facts were considered only to confirm that there was no reason to deviate from that uniform conclusion. Thus, proper venue was in the D.C. Circuit, not the “local” court of appeals for the petitioner. The Court emphasized that the characterization of the “action” must be grounded in the statutory authority underlying the EPA action, regardless of whether the agency aggregates multiple decisions into omnibus notices. The Court further held that EPA’s rationale regarding venue — if stated in its decision — should be reviewed de novo.

Oklahoma v. EPA: In an 8 – 0 opinion (Justice Alito recused), also authored by Justice Thomas, the Court applied the Calumet framework to hold that EPA’s aggregate disapprovals of individual state SIPs addressing cross-state ozone pollution were regionally applicable actions. The Court rejected EPA’s argument that a shared statutory interpretation and analytical approach were the “primary drivers” of its decisions. Instead, it found that the agency’s determinations turned on fact-specific, state-by-state assessments, rendering the actions locally applicable. The Court distinguished the case from Calumet, emphasizing that EPA’s disapprovals of the SIPs were grounded primarily in individualized, factual evaluations applicable to each individual state at issue. As no nationwide factor dictated the outcome, venue for each individual SIP decision would lie in the applicable regional court of appeals. (The Court did not address the potential for multiple courts of appeals to hear challenges to the overarching decision document and whether such challenges could or should ultimately be consolidated in just one circuit court).

Key Takeaways

• Different Litigants, Different Implications: Calumet centralizes framework SRE challenges in the D.C. Circuit, limiting regional challenges. Review of individual SRE decisions is likely appropriate in a regional circuit, but it will depend on the nature of the review. Now that the Fifth Circuit decision is vacated and no longer controls EPA’s substantive approach to deciding SREs, EPA may move forward on long-pending SRE petitions using the D.C. Circuit standard (discussed here) and could initiate rulemaking or guidance to clarify its exemption framework. In contrast, Oklahoma allows states to challenge SIP disapprovals closer to home, potentially enhancing their litigation leverage. More broadly, Calumet clarifies the circumstances in which individual or aggregate EPA decisions that are locally or regionally applicable nonetheless fall within the statutory exception of having a “nationwide scope or effect” and must be challenged in the D.C. Circuit.
• Two-Step Venue Test: In both cases, Justice Thomas articulated a new two-part test: (1) determine whether the EPA action is facially applicable at a national or local level; and (2) if local, assess whether the agency’s reliance on a nationwide determination is the “primary driver.” This approach drew criticism in a dissent and concurrence from Justice Gorsuch, who argued that the majority improperly conflated EPA’s “determination” with the rationale underlying such a determination.
• Broader Impact on Clean Air Act Litigation: The rulings suggest that certain EPA actions grounded in “nationwide rationale” may be subject to centralized review in the D.C. Circuit. While venue already lies in the D.C. Circuit for inherently nationwide actions, such as NSPS and NESHAPs, these decisions may expand that scope, albeit cabined to a limited set of circumstances. Specifically, they are likely to affect (1) single state/facility actions with a “nationwide rationale,” (2) aggregated individual decisions (such as the omnibus 2022 SRE action in Calumet), and (3) rules that apply to a regional subset of states (such as EPA’s cross-state air pollution rule). However, what constitutes a “nationwide rationale” under the Court’s framework — and whether that rationale is the “primary driver” of the agency’s action — remains to be fully clarified.

These paired rulings clarify — but also arguably leave some gaps in — the path for Clean Air Act litigation. Regulated entities and states should monitor EPA’s next steps on SRE petitions, SIPs, and related rulemakings. Going forward, not only the substance but also the reasoning behind EPA actions may determine where legal battles are fought.

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