The U.S. Supreme Court has ordered that the U.S. Environmental Protection Agency cannot begin implementing its rule to reduce greenhouse gas emissions from powerplants until a case pending in the U.S. Court of Appeals for the District of Columbia Circuit is resolved.

The high court on Feb. 9 issued the 5-4 ruling placing a temporary stay on the regulation, which the Obama administration calls the Clean Power Plan.

The ruling is a setback for supporters of the rule, which, they say, is one of the administration’s key strategies for addressing climate change.  The plan seeks to trim carbon emissions by 30% by 2030 and requires states to develop plans to begin achieving reductions in 2020. The initial state plans are due in September.

The appeals court issued an order on Jan. 21 rejecting opponents’ request to place a stay on implementing the rule. But the opponents—29 states, several utilities and industry groups—petitioned the Supreme Court on Jan. 28 to stay the rule.

Although the rule has many opponents, some states, renewable-energy companies and electric utilities have said they support the plan, or have intervened in support of EPA as it defends the regulation.

Supporters of the rule say they are disappointed with the Supreme Court’s decision but add that they believe the administration ultimately will prevail in the appellate court.

Bob Perciasepe, president of the Center for Climate and Energy Solutions, said in a statemen: “The Supreme Court has made clear in previous rulings that EPA has the authority to regulate greenhouse gases. Whether or not the court ultimately upholds this particular rule, the need to cut carbon emissions will remain, and states need to figure out the most cost-effective ways to do that.”

Bill Becker, executive director of the National Association of Clean Air Agencies, adds, “Almost every state in the country has been working tirelessly over the past two years in preparing Clean Power Plan strategies. We fully expect that many of these the states will continue their efforts to reduce greenhouse gas emissions under their own legal authorities.”

Critics applauded the Supreme Court for delaying implementation of the rule until the legal questions are resolved.

Mike Duncan, president and CEO of the American Coalition for Clean Coal Electricity, which includes coal companies and utilities, said in a statement, “The stay is a signal the Supreme Court has serious concerns with the Clean Power Plan. We’re optimistic the [plan] will ultimately be rejected.

Jeff Connor, interim CEO of the National Rural Electric Cooperative Association, a petitioner in the appeals court case, said in a statement: “Charging ahead with implementation of the Clean Power Plan would have caused immediate and irreparable harm to America’s electrical co-ops.”  He added that the if the rule is upheld it could affect electrical co-ops' ability to provide affordable and reliable electricity.

A ruling by the appellate court is expected later this year.