Congressman Henry Waxman issued a subpoena March 13 to require the Environmental Protection Agency to turn over documents regarding its decision to deny California the power to regulate greenhouse gas emissions from cars and trucks.

Waxman, chairman of the House Government Reform and Oversight Committee, announced the subpoena after failed negotiations to get the EPA to turn over the documents.

“These documents must be provided to the committee because they are relevant to the examination of the administration’s decision to reject California’s efforts to reduce greenhouse gas emissions from automobiles,” Waxman told the Associated Press. “The desire to conceal embarrassing facts is not a valid legal basis for withholding these documents from the committee.”

The subpoena, the second issued by Waxman to the EPA about the decision, comes after EPA Administrator Stephen L. Johnson denied the state's request for a waiver from the Clean Air Act in December.

The California law would have required makers of cars and light trucks to slash greenhouse gas emissions by 30% by 2016. Johnson has said he preferred Congress’ new fuel efficiency standards, which provide a national standard.