In a 6-2 decision authored by Justice Thomas, the Supreme Court held in consolidated cases Oklahoma v. EPA and PacifiCorp v. EPA that the Environmental Protection Agency (EPA)'s disapprovals of 21 individual state implementation plans (SIPs) under the Clean Air Act (CAA) are "locally or regionally applicable" actions, and, as such, must be challenged in their respective regional circuit courts—even when the EPA publishes them in a single, consolidated Federal Register notice.
As summarized in our April issue, in 2025, the EPA disapproved the SIPs, finding that they failed to meet the "good neighbor" provision of the CAA, which requires states to prevent their emissions from affecting air quality in downwind states. The EPA grouped these disapprovals in one Federal Register notice. When affected states and industry stakeholders filed suits in various regional circuits, the EPA successfully argued in the Tenth Circuit that the consolidated publication rendered the action "nationally applicable," requiring exclusive review in the D.C. Circuit under 42 U.S.C. § 7607(b)(1).
That statute distinguishes between:
- "Locally or regionally applicable" actions, which must be challenged in the appropriate regional circuit, and
- "Nationally applicable" actions—or regional actions based on a "nationwide scope or effect"—which are reviewed in the D.C. Circuit if the EPA makes and publishes that finding.
Applying the Court's framework from EPA v. Calumet Shreveport Refining, LLC—decided the same day:
- Each Disapproval Is a Separate Action: The Court held that each disapproval of an SIP is its own distinct, regionally applicable action—even when the EPA groups them for publication. The statutory venue analysis depends on the substance of the action, not how the agency chooses to package its decisions.
- No Justified Finding of Nationwide Scope: Although the EPA published a finding of nationwide scope or effect, the Court found that the agency's actions were not actually based on such a rationale. Instead, the approvals relied on individualized, state-specific determinations. Under Calumet, the national scope exception applies only if it is the primary basis for the agency's decision. Here, the EPA evaluated each plan on its own merits based on "a number of intensely factual determinations" for each state.
The decision reinforces that venue determinations turn on the substantive basis of EPA actions rather than their form, ensuring that challenges to state-specific environmental decisions can be heard at home in the circuits most familiar with regional conditions and concerns.
Justice Gorsuch, joined by Chief Justice Roberts, concurred in the judgment but expressed disagreement with the majority's reasoning. Specifically, they took issue with the majority's view that the EPA must establish that some nationwide conclusion qualifies as the "primary driver" of the challenged action, arguing that amounts to an ambiguous, judicially devised test without an objective standard. Instead, they opined, the CAA requires the EPA to approve or disapprove SIPs for individual states and does not call for a nationally applicable action or determination of nationwide scope or effect by the EPA to do so. Thus, they reasoned, SIP denials are regional actions under the text of the statute. Justice Alito took no part in the decision.
Takeaways:
- Venue Is Based on Substance, Not Packaging: The EPA cannot sidestep regional judicial review by combining multiple state-level actions into one administrative publication. Courts will look to the nature of the agency's decisions, not their format.
- Primacy of Regional Circuits: States and stakeholders can challenge disapprovals of state implementation plans in their home circuits, ensuring review by courts familiar with local and regional environmental conditions.
- Limits on Nationwide Scope Claims: A conclusory "nationwide scope or effect" label is insufficient. The EPA must demonstrate that such a determination truly underlies its decision to shift venue to the D.C. Circuit.
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