The U.S. Environmental Protection Agency cannot freeze implementing a rule requiring oil and gas companies to fix methane leaks in their equipment, a federal appeals court ruled on Monday in a setback for President Donald Trump’s push to cut environmental regulations.

The EPA on June 5 announced a stay in the rule, which would have required drillers and transporters to start reporting and fixing any methane leaks they found in wells and transfer stations, after EPA Administrator Scott Pruitt wrote in an April 18 letter the agency intended to reconsider imposing it. But the U.S. Court of Appeals for the District of Columbia Circuit said the agency did not have the authority to halt the rule during those deliberations.

The EPA’s stay “is essentially an order delaying the rule’s effective date, and this court has held that such orders are tantamount to amending or revoking a rule,” Judges David Tatel and Robert Wilkins wrote. The third member of the three-judge panel, Judge Janice Rogers Brown, dissented.

“We are reviewing the opinion and examining our options,” an EPA spokeswoman said in a statement to Reuters.

The court’s ruling came in response to a lawsuit filed June 5 by green groups that opposed the EPA’s stay of the rule. The groups, including the Natural Resources Defense Council, Environmental Defense Fund, Sierra Club and other environmental organizations, argued the EPA did not follow procedures detailed in the 1970 law known as the Clean Air Act when it froze the rule.

“This is a big win for public health and a wake-up call for this administration,” said Tim Ballo, a staff attorney for the group Earthjustice, one of the groups participating in the case.

David Doniger, director of the NRDC’s Climate and Clean Air Program, said other courts could follow suit on pending challenges to Pruitt’s suspensions of a slew of EPA rules, including those governing methane leakage from landfills and protections from chemical accidents and pesticides.

“This is the first court to rule and the first to strike him down,” he said.

Pruitt has vowed to make conditions more favorable for oil, gas and coal companies. In his April letter, he said he had begun examining a set of EPA regulations known as the Clean Power Plan following an executive order by Trump to “suspend, revise, or rescind” rules that “potentially burdened the development” of U.S. energy sources.

The case is Clean Air Council v. Scott Pruitt, U.S. Court of Appeals, D.C. Circuit, 17-1145.

(Reporting by Emily Flitter in New York; Editing by Lisa Shumaker)