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Trump’s EPA suffers its first major loss in court.

A federal appeals court on Monday ruled that Environmental Protection Agency Administrator Scott Pruitt is not allowed to delay an Obama-era regulation limiting methane pollution from the oil and gas industries. Pruitt announced last month that he would halt the rule for two years, meaning oil and gas companies would not have to place strict limits on emissions of methane, which is the main component of natural gas and a powerful greenhouse gas.

Pruitt—a longtime ally of the fossil fuel industry and a climate-change denier—had attempted to delay the rule at the request of oil and gas industry players, who said they did not have enough time to comment on the regulations, which were finalized in May 2016. But the U.S. Court of Appeals for the District of Columbia ruled that the industry had “had ample opportunity” to weigh in on the rule, and therefore EPA’s decision to delay it was “arbitrary and capricious” under the law.

Environmental groups say the decision suggests Pruitt might have trouble with his slow-walking strategy for dismantling Barack Obama’s climate and environmental legacy. For instance, Pruitt also announced a one-year delay for states to meet the requirements of Obama’s ground-level ozone rule, which limited the amount of emissions that cause smog. “The ruling recognizes that EPA lacks the authority to simply scrap these critical protections,” David Doniger, a director at the Natural Resources Defense Council, said in a statement.

However, as Mother Jones’ Rebecca Leber noted, Pruitt is not out of options if this legal strategy fails. There’s much more he can do beyond delaying regulations to meet his goal of weakening America’s environmental policies.