U.S. judges raise doubts about early challenge for EPA carbon rules

WASHINGTON (Reuters) - In the first legal test of the Obama administration's plan to limit greenhouse gas emissions from power plants, two of three federal judges hearing a challenge to the regulations on Thursday expressed skepticism about weighing in before they are formally adopted.

More than a dozen states and Murray Energy Corp [MUYEY.UL] filed lawsuits last year challenging the administration's proposal, which would require the U.S. power sector to slash carbon dioxide emissions by 30 percent from 2005 levels.

Judges Thomas Griffith and Brett Kavanaugh, both of the U.S. District Court of Appeals for the District of Columbia, questioned whether it was too early to address whether the Environmental Protection Agency had the legal authority to regulate power plants as proposed under the administration's Clean Power Plan.

"We could guess what the final rule looks like, but we're not usually in the business of guessing," Griffith said.

The states and Murray Energy, facing potentially substantial compliance costs, took the unusual step of suing the government before the rules were final.

The move poses a legal quandary for the court, which typically does not rule on regulations that are not final.

The three judges set to rule on the cases are all Republican appointees.

The administration's Clean Power Plan is the centerpiece of President Barack Obama's effort to address climate change in his final term in office.

The states and Murray Energy argued that EPA can not regulate power plants as proposed because the facilities are already covered under the Clean Air Act by the Mercury and Air Toxics Standards.

They said allowing the carbon rules to move forward would amount to double regulation and urged the court to act now to prevent harm to states that can not be undone.

(Reporting by Ayesha Rascoe)