Here’s why: It had long been clear that many states would challenge the EPA regulations. Within hours of the rules’ final publication last fall, two dozen states sued the government to stop their implementation; eventually, 29 states in total joined the lawsuit. But some climate advocates hinted that these legal protests wouldn’t matter. Simply by existing, they said, the rules communicated that America was moving its energy system away from fossil fuels. Global investors would have to follow suit, they said, and divest from fossil fuels. In other words, even if the Supreme Court eventually struck the Clean Power Plan down, the damage would be done.

The idea wasn’t for naught. Coal stocks tanked over the last year, and many of the largest American coal companies have filed for bankruptcy. In fact, opponents of the plan cited this exact effect in their brief: The “EPA hopes that, by the time the judiciary adjudicates the legality of the Power Plan, the judicial action will come too late to make much if any practical difference,” said one brief from the Harvard law professor Laurence Tribe. He called the plan a “targeted attack on the coal industry.”

The court’s stay means that that effect might go on pause, at least domestically. It could also push the entire timeline for the regulations forward. Previously, states had to submit compliance plans by this summer, though they could request an extension to 2018. But now, the D.C. circuit isn’t scheduled to hear the EPA’s case until June, and any appeal wouldn’t wind up in front of the Supreme Court until the fall at the earliest. By that time, of course, the White House will have changed hands—which means, short of defending this regulation, the Obama administration is running out of ways to push climate in the direction it wants.

How much danger is the Clean Power Plan ultimately in? The Court’s stay is so “unprecedented”—even The New York Times calls it that, in stolid reporter voice—that no one knows for sure.

On the one hand, the high court has never before blocked federal regulation while a case about it was being heard by an appeals court. On the other, the Supreme Court is the reason why the Clean Power Plan could exist in the first place. The EPA issued the rules under the Clean Air Act, a 1970 statute that forms much of the basis of federal environmental law and which requires the government to limit “air pollutants” that might harm public welfare. In 2007, the Supreme Court ruled that “greenhouse gases fit well within the Act’s capacious definition of ‘air pollutant’” and thus the EPA was obligated to regulate them. The Bush administration’s EPA never quite got around to it. But the Obama administration eventually did, and quite ambitiously. Since 2010, as well, this president’s EPA has won most of its fights about the act.