In Ohio v. Environmental Protection Agency, the Supreme Court voted 5-4 on June 27, 2024 to temporarily block the EPA’s “Good Neighbor Plan,” a federal rule aimed at cutting air pollution that drifts from one state into another. The Court did not decide whether the rule was legal. It issued a stay, pausing enforcement while the D.C. Circuit Court of Appeals reviews the full challenge.1Supreme Court of the United States. Ohio v. Environmental Protection Agency
What the Good Neighbor Plan Was Meant to Do
The Clean Air Act’s Good Neighbor Provision requires each state to prohibit emissions that significantly worsen air quality in downwind states.2Office of the Law Revision Counsel. 42 USC 7410 – State Implementation Plans for National Primary and Secondary Ambient Air Quality Standards States write their own plans first; if a state fails to submit one or the EPA finds it inadequate, the agency can impose a federal plan.3US EPA. Cross-State Air Pollution – Section: The “Good Neighbor” Provision
In March 2023, the EPA finalized its Good Neighbor Plan for the 2015 ozone air quality standards. The agency had reviewed submissions from 23 states, found them inadequate or missing entirely, and issued a single federal plan covering all 23. The rule targeted nitrogen oxide emissions from power plants, cement kilns, and industrial boilers, requiring covered facilities to run existing pollution controls more effectively starting in 2023 and to install widely available additional controls by 2026.4United States Environmental Protection Agency. Good Neighbor Plan for the 2015 Ozone NAAQS – Compliance for Industrial Sources
Why Ohio and Other States Sued
Ohio led a coalition of states and industry groups arguing that the EPA had short-circuited the Clean Air Act’s state-first structure by rejecting state plans and immediately imposing federal controls. They also argued the agency acted arbitrarily by not giving states enough time to revise their plans and by understating the compliance costs facing power plants and industrial facilities.
The challenges landed in several federal appeals courts. Before the Supreme Court ever took the case, circuit courts had already blocked the plan in 12 of the 23 states, leaving only 11 still covered by the rule when the justices weighed in.5US Environmental Protection Agency. EPA Response to Judicial Order Granting Applications to Stay the Good Neighbor Plan Overview Fact Sheet
What the Majority Held
Justice Gorsuch wrote the majority opinion, joined by Chief Justice Roberts and Justices Thomas, Alito, and Kavanaugh. The Court’s central concern was that the EPA had never adequately explained how the plan could function as designed once it applied to barely half the states it was built around. The plan’s emissions budgets and cost thresholds had been calculated on the assumption that all 23 states would participate. Once 12 dropped out under earlier court orders, the majority reasoned, the entire framework rested on assumptions the EPA had not revisited. On that “failure to explain” theory, the majority found the challengers likely to succeed and granted the stay.1Supreme Court of the United States. Ohio v. Environmental Protection Agency
Combined with the earlier circuit stays, the ruling meant the Good Neighbor Plan was now paused in every one of the 23 states it originally covered.
Justice Barrett’s Dissent
Justice Barrett dissented, joined by Justices Sotomayor, Kagan, and Jackson. She called the majority’s reasoning an “underdeveloped theory” unlikely to hold up when fully litigated and criticized the Court for granting emergency relief in a “fact-intensive and highly technical case without fully engaging with both the relevant law and the voluminous record.”6Supreme Court of the United States. Ohio v. Environmental Protection Agency – Dissent
Her substantive points cut in several directions. The EPA’s methodology for setting emissions limits, she noted, drew on nationwide industry data rather than state-specific inputs, so the number of participating states did not actually change the pollution limits for any individual facility. The agency had confirmed its methodology was “independent of the number of states included in the Plan.” Barrett also flagged a procedural problem: under the Clean Air Act, challengers can raise in court only objections they first raised during public comment, and the “failure to explain” theory could not have been raised then because the court stays that produced the mismatch had not yet happened.6Supreme Court of the United States. Ohio v. Environmental Protection Agency – Dissent
Barrett wrote that the stay “leaves large swaths of upwind States free to keep contributing significantly to their downwind neighbors’ ozone problems for the next several years,” while the majority’s theory, if accepted, would only require the EPA to confirm what she said was already apparent from the record: it would have issued the same plan regardless.
What Has Happened Since the Stay
The stay sent the case back to the D.C. Circuit for full review, but the political ground shifted before that review could conclude. The incoming administration in 2025 signaled it would not defend the Good Neighbor Plan, and in March 2025 the EPA announced it was rolling the rule back. By January 2026, the agency had proposed approving the same state plans it previously rejected, which would let upwind states avoid the stricter federal pollution limits entirely.
The practical effect is that the Supreme Court’s legal questions have largely been overtaken by policy. Even a D.C. Circuit ruling upholding the plan would run into an EPA now working to withdraw it. For downwind states counting on federal intervention to address pollution crossing their borders, the gap created by the stay looks more permanent than temporary.
Where Ohio v. EPA Fits in the Court’s Recent Agency Cases
The decision did not create new legal doctrine, but it fit a pattern. The same Supreme Court term produced Loper Bright Enterprises v. Raimondo, which overturned the Chevron doctrine that had required courts to defer to agencies’ reasonable readings of ambiguous statutes; SEC v. Jarkesy, which limited agency enforcement through administrative tribunals; and Corner Post v. Board of Governors, which expanded the window to challenge older regulations.7Justia. Ohio v. Environmental Protection Agency, 603 US (2024)
Read together, these rulings tighten judicial oversight of the executive branch and raise the legal risk agencies take on when issuing ambitious regulations. For the EPA in particular, Ohio v. EPA alongside the earlier West Virginia v. EPA signals that courts will look closely at broad environmental rules, especially where the agency is accused of moving without clear congressional authorization or of skipping past procedural safeguards.