The court's stay of a climate-change rule leaves the president's environmental legacy in limbo until after he leaves office.

The fact that the court's 5-4 decision to halt implementation of the regulations came in a ruling that attracted the vote of swing justice Anthony Kennedy was an ominous sign for the administration and environmentalists, experts said. In 2007, Kennedy provided the key vote for a 5-4 decision requiring the Environmental Protection Agency to regulate carbon dioxide as a pollutant. Now, he seems skeptical that the means the Obama administration chose to do that was a legally valid one. "You have to be worrying, [in the White House] that you’ve lost Justice Kennedy at this point," said Brendan Collins, an environmental law attorney with the firm of Ballard Spahr.