“Legal experts are confident that the courts will uphold the Clean Power Plan,” said David Waskow, the international climate director at the World Resources Institute, in a statement. “The U.S. administration has been crystal clear about its ongoing support for the Paris Agreement and commitment to achieve its 2025 climate targets.”

That might be overstating the case. Some advocates had hoped that even before the Clean Power Plan kicked in in 2022, it would shape how energy markets worked. The EPA could regulate, the story went, through the power of positive thinking. Some of this is still true: Renewable energy will keep getting cheaper, and U.S. coal companies are doomed no matter what.

But the Court’s stay diminishes that effect, at least in the short term. November’s presidential election will now either ratify or ruin Obama’s fight to mitigate climate change. No remaining Republican candidate for president supports imposing federal limits on greenhouse-gas emissions. If the GOP takes the White House, it could drop the case, and use its control of the executive and legislative branch to help fossil fuel companies by offering subsidies.

But if Democrats manage to retain the presidency, and a future administration defends the deal, then a significant chunk of Obama’s climate legacy will be left to the Supreme Court to decide. Should climate-concerned people really still trust the Clean Power Plan will all work out then? And if Obama’s EPA regulations die, will the global accord on climate that he fought for perish too?

* * *

Not everyone is zen about the Supreme Court’s stay. Seth Jaffe, the former president of the American College of Environmental Lawyers, had predicted in December the Court would not stay the regulation. When it did, earlier this week, he took it as a sign of doom. The Clean Power Plan “is on very shaky ground at this point,” he wrote.

“One has to conclude that five justices have decided that the rule must go,” he said. The terms of the stay are so extraordinary, so unusual, that it means something is up.

“I hope [the advocates of the regulation] win, but my neutral-objective-advice side says this is a hard one for them,” he told me on Thursday. “The advocates can talk all they want about how they have deference, and the Supreme Court has given deference to the EPA in the past. But this really is a big rule that is largely unprecedented.”

Deference is the idea that the courts should give federal agencies some leeway in executing their regulatory duties. In the last 30 years, deference has been applied to labor law and net neutrality, but it takes its name from a 1984 case about the Clean Air Act—the same piece of legislation that the EPA is using today.

What’s legally controversial with the Clean Power Plan is its two-step approach. First, the plan sets regulatory limits on the amount of carbon dioxide that state electricity plants can emit. Second, it establishes a set of incentives and regulations—it calls them “building blocks”—to entice state utilities to switch away from coal-fire power generation toward natural gas, nuclear power, and renewables.