Oklahoma v. EPA: Individual SIP Disapprovals Are Regionally Reviewable – Refining the Venue Framework Under CAA §7607(b)(1)

1. Introduction

In Oklahoma v. Environmental Protection Agency, 605 U.S. ___ (2025), the Supreme Court clarified where legal challenges to the Environmental Protection Agency’s (EPA) disapproval of State Implementation Plans (SIPs) must be filed. At stake was the correct venue under §7607(b)(1) of the Clean Air Act (CAA) when EPA, in a single omnibus rule, rejected 21 state SIPs submitted pursuant to the “Good Neighbor” provision designed to curb cross-state ozone pollution.

Oklahoma, Utah, and industry petitioners filed their challenges in regional courts of appeals. The Tenth Circuit, alone among the five circuits to consider the venue question, transferred the cases to the D.C. Circuit, reasoning that EPA’s omnibus rule was a single, “nationally applicable” action. The Supreme Court reversed, holding that:

Each individual SIP disapproval constitutes its own “action.”
Such actions are “locally or regionally applicable” and presumptively belong in the appropriate regional circuit.
The “nationwide scope or effect” exception does not apply unless the nationwide determination is the primary driver of the action—something the Court found lacking here.

2. Summary of the Judgment

Holding: EPA’s disapprovals of Oklahoma’s and Utah’s SIPs are locally or regionally applicable actions. Venue therefore lies in a regional circuit, and the cases are remanded accordingly.
Vote: 6–2 (Justice Thomas for the Court; Justice Alito did not participate. Justice Gorsuch, joined by Chief Justice Roberts, concurred in the judgment on different reasoning.)
Key Points:
- Aggregation of multiple SIP decisions into a single Federal Register notice does not transform them into one nationally applicable action.
- To trigger the “nationwide scope or effect” exception, a nationwide determination must be the chief rationale—not merely one of several analytical tools.
- The Court relied heavily on its companion case, EPA v. Calumet Shreveport Refining, L.L.C., decided the same day.

3. Detailed Analysis

3.1 Precedents Cited and Their Influence

EPA v. Calumet Shreveport Refining (2025)
Provided the two-step framework for determining venue: (1) identify the “action” and classify it as nationally versus locally/regional; (2) apply the “nationwide scope or effect” exception. Oklahoma v. EPA extends this framework to SIP disapprovals.
American Road & Transportation Builders Ass’n v. EPA (D.C. Cir. 2013)
Described SIP approvals as the “prototypical” locally or regionally applicable actions—language adopted by the Court for SIP disapprovals.
Texas v. EPA (5th Cir. 2016) & West Virginia v. EPA (4th Cir. 2024)
Highlighted the “intensely factual” nature of SIP evaluations, reinforcing the Court’s conclusion that no single nationwide rationale controlled.
Other Citations: United States v. Detroit Timber & Lumber Co. (syllabus precedent), Ohio v. EPA (context for Good Neighbor provision), and earlier CAA venue cases that shaped the statutory landscape.

3.2 The Court’s Legal Reasoning

Step One – Identifying the “Action”

Section 7607(b)(1) itself lists “action in approving … any implementation plan under §7410” as an example of a locally or regionally applicable action. Because approvals and disapprovals are “opposite sides of the same coin,” each SIP disapproval is likewise its own discrete “action.”

Crucially, the Court stressed that Congress—not EPA—defines what an “action” is. Therefore, EPA’s stylistic choice to publish 21 disapprovals in one omnibus rule does not fuse them into a single action for venue purposes.

Step Two – The “Nationwide Scope or Effect” Exception

An action qualifies for D.C. Circuit review under the exception only if:

It is based on a determination of nationwide scope or effect; and
EPA makes and publishes such a finding.

Although EPA published the requisite finding, the Court held the first prong unsatisfied. A nationwide determination must be the “primary explanation and driver” of the action. Here, EPA’s decisions rested on “intensely factual, state-specific” analyses—e.g., Oklahoma’s reliance on Texas emissions data and Utah’s treatment of Colorado contributions. The nationwide heuristics (updated 2016 modeling, 1% contribution threshold, etc.) were merely analytical tools, not dispositive rationales.

3.3 Practical and Doctrinal Impact

Venue Landscape: Challenges to individual SIP actions will now reliably proceed in regional circuits, reducing forum-shopping fears and diversifying judicial oversight of EPA decisions.
Agency Rulemaking Strategy: Omnibus aggregation will no longer guarantee D.C. Circuit venue. Agencies must anticipate piecemeal regional challenges when their actions turn on state-specific facts.
Litigation Tactics: States and industries may prefer circuits perceived as more sympathetic, potentially leading to split decisions and expedited Supreme Court review.
Federalism Emphasis: By reaffirming state-focused review, the Court bolsters cooperative-federalism principles embedded in the CAA.
Clarified Test for Nationwide Scope: The “primary driver” standard, now applied twice in one term (Calumet and Oklahoma), will govern future statutory schemes with similar venue bifurcations.

4. Complex Concepts Simplified

State Implementation Plan (SIP): A state’s blueprint, approved by EPA, showing how it will meet federal air quality standards.
Good Neighbor Provision: Requires states to ensure their emissions do not significantly contribute to downwind states’ failure to meet NAAQS (National Ambient Air Quality Standards).
“Locally or Regionally Applicable” vs. “Nationally Applicable”:
- Locally/Regionally: The rule binds only specific states or regions on its face.
- Nationally: The rule binds parties across the entire country.
Nationwide Scope or Effect Exception: A statutory safety valve sending even local actions to the D.C. Circuit when a controlling, nationwide rationale underlies the decision and EPA so states.
Four-Step Framework (EPA terminology): EPA’s internal method for analyzing whether an upwind state must reduce emissions under the Good Neighbor clause.

5. Conclusion

Oklahoma v. EPA cements a textual, state-centric approach to the CAA’s venue provision. By rejecting EPA’s attempt to secure exclusive D.C. Circuit review through procedural bundling, the Court safeguards regional access to judicial review and underscores that federal agencies cannot manipulate statutory venue through formatting choices. Future challenges to environmental regulations—particularly those involving discrete, state-specific determinations—will be litigated where the pollution (and the politics) live: closer to home.

Combined with Calumet, the decision provides a clear, two-step roadmap for courts and litigants, ensuring that nationwide venue determinations turn on the substance, not the packaging, of EPA’s actions. The precedent will influence not only air-quality litigation but any statutory regime that couples national standards with local implementation.