[JURIST] The head of the US Environmental Protection Agency (EPA) on Tuesday refused to disclose a timeline for the agency's compliance with last year's Supreme Court ruling [JURIST report; opinion text] that the EPA has the authority under the Clean Air Act [text; EPA materials] to regulate the emission of "greenhouse gases," such as carbon dioxide, by automobiles. In its decision, the Supreme Court said that it was the responsibility of the EPA to determine whether greenhouse gases pose a public health danger under the Clean Air Act, so as to fall under EPA regulation. During testimony [statement, PDF] before the Senate Appropriations Committee [official website], EPA Administrator Stephen L. Johnson [official profile] said that his staff was "working on a myriad of issues," but avoided questions from Sen. Dianne Feinstein (D-CA) [official website] asking how many employees were working to comply with the Court's ruling. Johnson said that the Energy Independence and Security Act of 2007 [HR 6 materials; WH fact sheet], signed into law in December by President George W. Bush, made the EPA's response to the ruling more difficult than anticipated last year when he had promised to respond to the high Court's decision by fall of 2007.

Also during Tuesday's hearing, Johnson defended the EPA's controversial decision [JURIST report] last year to deny a request from California for a waiver that would have allowed the state to impose stricter greenhouse gas emissions standards on cars and light trucks. Johnson has said that a unified national standard for greenhouse gas regulation is preferable to a state-by-state network of regulations, pointing again to the Energy Independence and Security Act, which will require automakers to reach an industry-wide average fuel efficiency for cars, SUVs and small trucks of 35 miles per gallon by 2020. The California standards would have required car manufacturers to cut emissions by 25 percent from cars and light trucks, and 18 percent from SUVs, starting with the 2009 model year. The EPA has denied several requests [JURIST report] for a full explanation of the emissions waiver rejection. AP has more.