A three-judge panel for the U.S. Court of Appeals for the D.C. Circuit has ruled it is too soon to legally challenge the U.S. Environmental Protection Agency's proposed rule to trim carbon emissions from existing powerplants.

Judge Brett Kavanaugh said on June 9 that although industry groups, companies and states are "champing at the bit" to challenge EPA's proposal, expected to be made final this summer, the court lacks the authority to evaluate proposals that are not final.