Supreme Court hears dispute over whether bundled EPA disapprovals of state plans belong in DC or regional courts

The Supreme Court heard argument in Oklahoma v. Environmental Protection Agency about whether EPA’s bundled disapprovals of state implementation plans must be reviewed in the D.C. Circuit or in regional circuits where the states are located.

Oklahoma’s lawyer, Mansingh Hani, argued that “EPA actions to approve or disapprove state implementation plans are the prototypical action reviewed in the regional circuit,” and that the Clean Air Act’s venue provision directs courts to the statutory authority under which EPA acted rather than to the form of publication. Hani asked the Court to reverse the decision below and remand the case to the Tenth Circuit.

Why it matters: the Court’s decision will determine whether challenges to state-specific Clean Air Act decisions are litigated locally — where states and local facts are central — or centralized in the D.C. Circuit when EPA publishes a single Federal Register notice covering multiple states. That choice affects how uniformly national standards are reviewed, how litigants allocate briefing and resources, and whether consolidated national review could supplant regionally focused adjudication.

Counsel for EPA, Mr. Stewart, defended the agency’s position that some bundled actions may be funneled to the D.C. Circuit when the agency’s action is “based on a determination of nationwide scope and effect.” Stewart said the statutory channeling to the D.C. Circuit is Congress’s choice for centralized review of national issues, and argued that the practical effect of EPA’s four nationwide determinations (including the 1% screening threshold) meant that judicial review would focus on national criteria rather than solely on state-specific application.

The parties and several justices discussed a recurring technical detail in the agency’s analysis: a 1% contribution-screening threshold EPA used to distinguish states whose upwind emissions the agency deemed de minimis. Counsel for the states and intervenors pressed that EPA’s 1% threshold is not mandatory for states, that EPA gave state-specific reasons when it rejected alternative metrics, and that much of the ultimate decision-making required state‑by‑state factual analysis — for example, how regional geography or generation patterns affect downwind ozone contributions. As counsel put it, even after the nationwide criteria are applied, “those were all very state specific things that EPA had to adjudicate.” (Mansingh Hani)

Several justices probed whether a screening threshold or other nationwide criterion could be set so low that it would effectively determine the outcome in every state — a circumstance they said would more clearly qualify as a nationwide determination. Justice Kagan and others asked hypothetical questions about whether an extremely low threshold (for example, 0.01%) would make the action essentially national in scope; counsel acknowledged that an automatic, uniform rule that preordains outcomes in every state would be closer to the sort of nationwide determination Congress intended for centralized review.

The argument also turned on statutory interpretation. Oklahoma’s counsel and a number of state-side advocates urged a textual reading that places SIP approvals and disapprovals in the “local or regional” bucket of the statute’s second sentence, leaving only a narrow exception for truly national determinations. They warned that EPA’s bundling and reliance on preamble language could be used to manipulate venue and centralize local disputes in Washington.

The government responded that the statute contemplates centralized review for national issues arising in SIP litigation and that EPA anticipated significant challenges to the agency’s national criteria, not just to state‑specific applications. Stewart said EPA approved roughly 23 plans and disapproved about 21 in the contested Federal Register notices, and that those numbers reflected how the 1% threshold predicted approvals and disapprovals in practice.

The justices repeatedly pressed counsel on practical administration and deference. Several asked whether courts should give any deference to EPA’s view about which forum is appropriate; counsel for Oklahoma said the venue question is a legal one reviewed de novo, while other counsel allowed that some aspects of an agency’s published “finding” might be reviewable for reasonableness if the agency explicitly made such a finding.

The case raises two distinct but related legal questions: whether the statutory text — particularly the sentence that lists SIP approvals and disapprovals as locally or regionally applicable — controls venue, and whether an exception for actions “based on a determination of nationwide scope and effect” applies when EPA issues uniform criteria and then applies them to multiple states. The Court’s answer will determine whether future SIP challenges are litigated regionally or centralized in the D.C. Circuit.

The argument concluded with counsel saying the Court had full briefing and was prepared to decide the issue. “The case is submitted,” the bench announced.