Twenty-one states, the District of Columbia and a slate of cities petitioned the U.S. Court of Appeals for the District of Columbia on Oct. 1 to overturn the Environmental Protection Agency's repeal of greenhouse gas emission limits for coal- and natural-gas-fired power plants. The Democratic-led coalition, led by New York, frames the EPA's September action as an unlawful retreat from the federal government's core climate authority.

New York Attorney General Letitia James said the federal government is showing "callous disregard" for Americans' health and the environment. "Dismantling these protections is a betrayal of American families, and the stakes are too high to allow this administration to once again put profits over people," James said in a Thursday statement.

What does the EPA's repeal actually change?

The Biden-era rule — the Greenhouse Gas New Source Performance Standards — set emission limits on new and existing coal and gas facilities. The agency projects more than $300 billion in industry savings from scrapping the standard. EPA Assistant Administrator Aaron Szabo said in September that the move lets utilities "make the best decision for the ratepayers based on cost and cost savings, instead of being required to shut down facilities."

The plaintiffs counter that those savings ignore unpriced health and climate costs. The coalition argues the agency "unlawfully abandoned the pollution limits without properly considering reasonable alternatives."

Who joined the challenge?

The 21-state filing covers:

• New York (lead)
• Arizona, California, Colorado, Connecticut
• Delaware, Hawaii, Illinois, Maine
• Maryland, Massachusetts, Michigan, Minnesota
• New Jersey, New Mexico, North Carolina, Oregon
• Rhode Island, Vermont, Washington, Wisconsin

Pennsylvania's governor, the District of Columbia, New York City, Chicago, and the city and county of Denver joined the states. Together they represent roughly half of the U.S. population and most of the country's largest metropolitan electricity markets.

What happens on the parallel regulatory track?

The same coalition notified the EPA of its intent to sue over the agency's separate failure to regulate emissions from many existing gas-fired plants. A second rule proposed last month would lock the door further: it seeks to bar future administrations from regulating greenhouse gases from the power sector at all. The agency expects that proposal to be finalized in 2027.

How does this connect to the Supreme Court docket?

The state challenge lands one day before the U.S. Supreme Court convenes its new term. On Monday, justices will hear Boulder, Colorado's suit against oil and gas companies seeking damages for climate-related disasters. That case carries billions of dollars in potential exposure and signals how the high court may treat climate liability claims against fossil-fuel defendants.

What milestone decides the next move?

The D.C. Circuit's review sets the procedural clock. A likely stay request, a briefing schedule, and a merits decision by mid-2027 will determine whether the 21-state coalition can force the agency back to the rulemaking table before the separate power-sector restriction becomes final. Until then, utilities operate under the vacated GHG limits the Biden administration wrote and the Trump administration scrapped.