States opposing President Obama’s signature climate change plan are heartened by federal judges’ reactions to their constitutional objections to the plan during seven hours of oral arguments Tuesday, while supporters of the Clean Power Plan said challengers’ claims were overblown while voicing some reservation about calling the day a victory.

“The Clean Power Plan had a very good day. But we aren’t taking that to the bank just yet,” said David Doniger, the Natural Resources Defense Council’s climate director, after the arguments concluded. The NRDC is a top environmental supporter of the plan represented at the D.C. Circuit Court of Appeals.