The U.S. Court of Appeals for the D.C. Circuit’s decision to hear arguments in Clean Power Plan litigation was a “highly unusual” move, but doesn’t signal how judges might rule, a prominent environmental attorney told California Energy Markets.

Ballard Spahr's Brendan Collins said the court’s decision is “certainly a test of the importance of the issue,” but he also noted it is “not a substantive commentary on the merits of the [Environmental Protection Agency] rule.”

The case is widely expected to land at the Supreme Court following the appeals court’s ruling. The high court imposed a nationwide stay on the Clean Power Plan on Feb. 9.

Still uncertain is whether 10 or 11 judges would hear the arguments, Collins said, which could have a bearing on how the court rules. He characterized the court as an “interesting mix” of “conservative liberals and liberal conservatives.”

Collins said EPA’s drafting of the rule under Section 111(d) of the Clean Air Act was “very adaptive,” which he said complicates speculation on how the court might rule.