The Obama administration’s ambitious climate-change agenda suffered a significant obstacle yesterday, as the Supreme Court temporarily blocked its centerpiece regulation.

The Environmental Protection Agency’s Clean Power Plan would force states to cut their carbon emissions by 32 percent from 2005 levels over the next 15 years, a requirement expected to carry hundreds of billions in cost. It would also result in double-digit utility rate hikes for most Americans.

Twenty-nine states have challenged the regulation, also arguing that unless the Supreme Court issued a stay, they would have to begin immediately enacting sweeping and often irreversible changes. The Supreme Court’s 5-4 decision to grant that stay signals well-merited misgivings about the Clean Power Plan.

The Court has already reprimanded the EPA for other overreaching rules, with Justice Scalia recently writing: "When an agency claims to discover in a long-extant statute an unheralded power to regulate ‘a significant portion of the American economy,’ we typically greet its announcement with a measure of skepticism." 

The stay calls into question not only President Obama’s domestic environmental agenda but also his foreign policy goals. America’s commitment at the Paris Climate Conference centered on the Clean Power Plan, as did the U.S.-China emissions pact inked last year.

While the regulation’s final fate is yet to be determined, this is a major setback.