Washington — The Supreme Court on Thursday agreed to block an environmental rule that aims to curb air pollution and address harmful smog that travels from certain states into others while legal proceedings continue.

In a 5-4 decision, the court granted the request from Ohio, Indiana and West Virginia, as well as energy companies and industry groups, to pause the rule. Justice Neil Gorsuch authored the majority opinion. Joined by Chief Justice John Roberts and Justices Clarence Thomas, Samuel Alito and Brett Kavanaugh, Gorsuch said that the Environmental Protection Agency failed to reasonably explain its federal implementation plan for controlling ozone pollution.

The majority said that the GOP-led states and energy industry are likely to prevail in their legal challenge to the agency's so-called "good neighbor" plan. But Justice Amy Coney Barrett, in dissent, said that the court's decision to block enforcement of the rule is based on an "underdeveloped theory" that is unlikely to succeed.

The court's order, she said, "leaves large swaths of upwind states free to keep contributing significantly to their downwind neighbors' ozone problems for the next several years." Joining Barrett in her dissent were Justices Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson.

The dispute involved the Clean Air Act's good neighbor provision, which aims to address interstate pollution issues. The law requires the EPA to set federal standards for the amount of certain pollutants that can be safely in the air. When the agency sets air quality standards, states must submit implementation plans to meet them.

Ohio v. EPA

Under the good neighbor provision, plans from certain states must contain measures to curtail ozone pollution, helping "downwind" states like New York, Pennsylvania and Wisconsin that struggle to meet air quality standards by federal deadlines.

Federal law gives the EPA the power to approve a state's plan only if it meets all of the Clean Air Act's requirements. If the EPA determines a proposal doesn't do enough to reduce air pollution, it can reject it and implement a federal plan.

The EPA in February 2023 determined that 23 "upwind" states failed to submit adequate plans to comply with air quality standards that the agency strengthened in 2015. The agency announced the federal good neighbor plan one month later, establishing an emissions-control program for power plants, refineries and other large industrial sources in those 23 states, which the EPA said were contributing significantly to ozone pollution in other downwind states. 

Several of those states challenged the EPA's disapproval of their implementation plans, and federal appeals courts have preliminarily halted the disapproval for 12 of them while legal proceedings continue. The EPA, too, has paused the federal plan requirements for those dozen states: Alabama, Arkansas, Kentucky, Louisiana, Minnesota, Mississippi, Missouri, Nevada, Oklahoma, Texas, Utah and West Virginia.

In the 11 other states covered by the good neighbor plan, the requirements remain in place.

The EPA said in February that power-plant emissions fell by 18% in 2023 for the 10 states implementing the good neighbor plan: Illinois, Indiana, Maryland, Michigan, New Jersey, New York, Ohio, Pennsylvania, Virginia and Wisconsin. Requirements for industrial sources other than power plants for the 11th state, California, are set to take effect in 2026.

The case before the Supreme Court stemmed from a challenge to the good neighbor rule from Ohio, Indiana and West Virginia, as well as energy companies and industry groups. 

Filed in the U.S. Court of Appeals for the District of Columbia Circuit, the three states sought to halt implementation of the federal plan, but in September, a divided three-judge panel from the D.C. Circuit denied the requests. They sought emergency relief from the Supreme Court in October, and the justices heard arguments in February.

The EPA has warned that ozone pollution can cause respiratory issues, and long-term exposure can lead to asthma. Those most at risk are children whose lungs are still developing and the elderly. 

With a 6-3 conservative majority, the high court has been skeptical of federal regulatory power, particularly when it comes to environmental rules. The Supreme Court has ruled against the EPA in recent years in two cases involving the Clean Water Act and Clean Air Act.

In its most recent decision, in May 2023, a divided court curtailed the EPA's authority to regulate certain wetlands under the 1972 law. One year earlier, in June 2022, the Supreme Court ruled along ideological lines to limit the EPA's power to set rules for greenhouse gas emissions from power plants.

The Supreme Court is also weighing an effort to overturn its 40-year-old Chevron decision, which requires courts to defer to an agency's reasonable interpretation of ambiguous statutes. The legal doctrine has given agencies the ability to issue rules regulating a host of areas that touch on American life, including health care and the workplace.

Melissa Quinn

Melissa Quinn is a politics reporter for CBSNews.com. She has written for outlets including the Washington Examiner, Daily Signal and Alexandria Times. Melissa covers U.S. politics, with a focus on the Supreme Court and federal courts.

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