In 2004, the California Air Resources Board (CARB) adopted the nation’s fi rst regulations limiting the emission of greenhouse gases from new motor vehicles. The California rules require automakers to reduce greenhouse gas emissions from new motor vehicles sold in the state, beginning with the 2009 model year. By 2016, new vehicle emissions must decline by nearly 30 percent. Several other states have announced their plans to follow California’s lead, adopting the regulations as their own. Before these regulations can take effect, however, California must obtain a waiver of preemption under the Clean Air Act (CAA) from the U.S. Environmental Protection Agency (EPA). California politicians demand such a waiver forthwith, and EPA Administrator Stephen Johnson has promised a decision on the request by the end of 2007....