Utilities, industry groups and 29 states have asked the Supreme Court to delay implementation of the U.S. Environmental Protection Agency’s regulation to curb powerplants’ greenhouse-gas emissions.

Their Jan. 27 petition with the nation’s top court follows a Jan. 21 order from the U.S. Court of Appeals for the District of Columbia Circuit that held that planning and implementation of EPA’s Clean Power Plan could move forward while litigation challenging the rule plays out. 

The regulation calls for emissions reductions of 30% by 2030.

However, the court expedited the schedule for briefings and oral arguments in the case. With oral arguments scheduled for June 2, the court could issue a ruling in the case before states are due to file their initial implementation plans in September. 

The Jan. 21 order means that states must continue to develop plans to trim emissions from existing powerplants.

The petitioners contend that, unless the Supreme Court intervenes, numerous coal-fired plants will be shuttered within the next year, which could affect the reliability of the electric grid. They add that a stay of the rule is needed because states already are experiencing economic harm as they gear up to develop implementation plans.

The National Rural Electric Cooperative Association, a petitioner in the case, estimates that total compliance for electrical cooperatives in the U.S. could reach as high as $28 billion over the 2022-30 compliance period. “Immediate and irreparable harm already is occurring—and will continue—unless the [Supreme Court] halts the Clean Power Plan while separate litigation over its legality plays out,” said Jeffrey Connor, NRECA’s interim CEO, in a statement.

Environmental groups counter that the rule is needed to comply with the international goal to limit the average global temperature increase to 1.5° C over time.

David Doniger, director of the Natural Resources Defense Council’s climate and clean-air program, said the federal appeals court decision “green-lights work that most states have already begun to put the Clean Power Plan into action and signals to others that there is no excuse for holding back on the implementation.”

EPA finalized the rule in August 2015 but did not publish it in the Federal Register until Oct. 23. Several states and industry groups filed legal challenges with the appellate court immediately after the rule was published.