Oklahoma v. Environmental Protection Agency, , was a case before the Supreme Court of the United States that addressed where lawsuits challenging certain EPA actions must be filed. The Court held that when the EPA disapproves a state implementation plan (SIP) under the Clean Air Act, that decision is a local or regional action, not a national one. As a result, challenges must be brought in the appropriate regional federal appeals courts, rather than exclusively in the D.C. Circuit..
Background In 2015, the EPA updated the National Ambient Air Quality Standards (NAAQS) for ozone. Under the Clean Air Act, each state was required to submit a plan explaining how it would meet the new standards.
The EPA rejected 21 of these state plans, including those from Oklahoma and Utah. The agency said legal challenges could only be heard in the D.C. Circuit. Several states, mostly Republican-led, disputed this interpretation and filed lawsuits in other regional courts.
Decision
In a unanimous decision, the Court rejected the EPA’s position. The justices held that each EPA disapproval of a state’s plan is a separate, discrete action under Section 7607(b)(1) of the Clean Air Act. Because these actions are locally or regionally applicable, challenges must be filed in the corresponding regional courts of appeals.
The Court noted that the EPA had made a similar argument in EPA v. Calumet Shreveport Refining (2025), which the justices had already rejected earlier that day.
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