Supreme Court’s Clean Air Ruling Risks Enforcement Divide (1)

The US Supreme Court’s new standard for when the Environmental Protection Agency can move Clean Air Act enforcement disputes to the D.C. Circuit has the potential to create circuit splits and disparate rulemaking for clean air standards, legal observers say.

In an unanimous opinion written by Justice Clarence Thomas Wednesday, the high court raised the bar for the agency to steer challenges over ozone pollution State Implementation Plans to its preferred venue, the US Court of Appeals for the D.C. Circuit. Only EPA actions where “justification of a nationwide breadth is the primary explanation” can be transferred to that forum, the justices said.

Oklahoma v. EPA regarded SIP disapproval—part of the Biden administration’s “Good Neighbor” nationwide ozone plan—as a local or regional application of agency decision. The ruling could limit the effectiveness of the pollution program, because the new standard now allows those disputes to be heard anywhere in the country, environmentalists say.

The program governs nitrogen oxides pollution that travels across state lines to meet the EPA’s 2015 National Ambient Air Quality Standards.

“What we’re seeing is splintering of how this nationwide thing the EPA is modeling is getting assessed across the country,” said Zachary Fabish, a senior attorney with the Sierra Club. “We’re really running the risk of seeing disparate decisions,” and there are “enormous public health and equity problems with that,” he said.

Federal governance of interstate ozone migration is meant to ensure that states that present “do nothing SIPs,” can be held accountable for pollution traveling from their jurisdictions to “downwind” states, Fabish said.

With different circuits hearing cases and potentially offering different standards for how the EPA can scrutinize things like data and public comments, state plans may take longer to finalize and ultimately go into effect, he said.

An EPA spokesperson said in a statement that the agency is reviewing the decision.

Two-Part Program

The two-part Good Neighbor program directs the EPA to review states’ implementation plans to reduce pollutants to NAAQS levels, then offer a federal alternative if the agency deems the plan out of compliance.

Pending challenges to SIP disapprovals currently span six US appeals courts and include over a dozen states.

The Supreme Court blocked the second part of the Good Neighbor rule last year, finding that the EPA failed to explain how the traveling ozone plan would work with patchwork participation from states that managed to curb enforcement in separate legal battles.

The agency last updated the Good Neighbor program in December, saying the agency’s four-step analytical framework adequately determines state obligations and doesn’t require adjustments even with fewer states participating.

Still, with scattered orders across lower courts putting various SIP disapprovals on hold, the EPA can’t impose a federal alternative plan.

The Supreme Court’s latest decision means a uniform standard will likely take longer to implement.

“The Clean Air Act’s judicial review provisions are designed to ensure orderly court review that respects the Act’s vital, time-sensitive protections for public health,” Vickie Patton, general counsel for the Environmental Defense Fund, said in a statement.

‘Nationwide Scope’

The D.C. Circuit has long been the authoritative court for EPA rulemaking, and the Clean Air Act includes a “nationwide scope” exemption from deferring to hearing disputes in the other circuits on locally applied rules.

But the Supreme Court held that the agency led with “predominately fact-intensive, state specific analysis” while the nationwide contribution factors were “at most heuristics that aided EPA’s analysis, as opposed to the primary drivers of its disapprovals” for Oklahoma and Utah’s SIPs, which were the ones at issue in the case the justices heard.

The decision is an opportunity for the EPA to restructure its rulemaking to put enforcement of a nationally applicable standard first, as opposed to individualized review of pollution controls within state borders, said Brian Bunger, a land use and environment partner at Holland & Knight LLP who is not involved in the case.

“EPA can do the upfront work to structure their review” of state-submitted plans likes SIPs or small refineries exemptions “in a way that the court would say were in the national framework, as opposed to localized review,” he said.

The case is Oklahoma v. EPA, U.S., No. 23-1068, 6/18/25.