The D.C. federal appeals court's order Tuesday imposing a second, 60-day delay in a decision in the legal battle over the so-called Clean Power Plan has the plan's environmental defenders pondering a trip to the U.S. Supreme Court.

“I'm not sure what the next best move is,” said David Doniger of the Natural Resources Defense Council, which represents environmental and public health groups supporting the plan. “We haven't reached a decision yet on what to do and in which court to do it. It is a very odd situation.”

The “odd situation” is that the litigation was briefed and argued before the full U.S. Court of Appeals for the D.C. Circuit on Sept. 27, 2016 — nearly a year ago. But before that occurred, the Supreme Court in February 2016, in an unusual step, issued a stay of the plan. The stay, approved by a 5-4 vote, was to remain in place pending resolution of the legal challenges in the D.C. Circuit.