In December 2005, California petitioned EPA to let the state develop its own program and standards for regulating greenhouse gas emissions from vehicles. Under the Clean Air Act, the federal government holds the express right to regulate emissions but may grant waivers to states, which it often does. If EPA grants California's waiver request, 11 other states could follow suit.
Yesterday, EPA Administrator Stephen Johnson wrote California Governor Arnold Schwarzenegger stating EPA would make its decision by the end of 2007. That's two full years after the initial request.