Oklahoma v. Environmental Protection Agency

The Clean Air Act requires that EPA state implementation plan (SIP) disapprovals be reviewed in regional circuit courts rather than the D.C. Circuit when they are "locally or regionally applicable" actions not based on determinations of nationwide scope or effect. Justice Clarence Thomas authored the 6-2 majority opinion of the Court. The Court applied a two-step framework established in EPA v. Calumet Shreveport Refining to determine proper venue under the Clean Air Act’s venue provision. First, courts must identify the relevant EPA “action” and determine whether it is “nationally applicable” or “locally or regionally applicable.” An “action” under the statute means a particular exercise of EPA authority undertaken pursuant to a particular Clean Air Act provision, determined by reference to the underlying statutory provision rather than how EPA presents its decision. Here, EPA’s disapprovals of Oklahoma’s and Utah’s state implementation plans constitute separate “actions” because the Clean Air Act treats individual SIP approvals and disapprovals as discrete actions under Section 7410. Each SIP disapproval applies only to the specific state that proposed the plan, making them “locally or regionally applicable” actions—the prototypical example of such actions under the statute. Because the SIP disapprovals are locally or regionally applicable, the Court proceeded to the second step: determining whether the “nationwide scope or effect” exception applies to require D.C. Circuit review. This exception requires that EPA’s action be “based on a determination of nationwide scope or effect” and that EPA find and publish this basis. Although EPA made the required finding, the Court held that EPA’s disapprovals were not actually based on determinations of nationwide scope or effect. The exception applies only when “a justification of nationwide breadth is the primary explanation for and driver of EPA’s action.” Here, EPA’s disapprovals resulted from predominantly fact-intensive, state-specific analysis of each SIP’s contents, producing unique lists of deficiencies for each state. The four nationwide determinations EPA cited—including use of updated modeling and a 1% contribution threshold—were merely analytical tools that aided EPA’s review rather than primary drivers of the disapprovals. Justice Neil Gorsuch authored a concurring opinion, joined by Chief Justice John Roberts, agreeing with the judgment but following a different analytical path as explained in their dissenting opinion in a companion case, Environmental Protection Agency v. Calumet Shreveport Refining, LLC.