On December 12, 2007, U.S. District Court Judge Anthony Ishii ruled against a group of automobile manufacturers challenging California’s authority to set and implement greenhouse gas emissions standards for motor vehicles. The auto industry had argued that the state's proposed regulations amount to setting fuel efficiency requirements for new vehicles, and that such efficiency standards can be set only by the federal government - specifically, the Department of Transportation's National Highway Traffic Safety Administration under the Energy Policy and Conservation Act. A similar ruling was issued earlier this year in Vermont against automobile industry plaintiffs challenging that state’s authority to adopt California’s vehicle emissions standards. California’s proposed standards would be gradually phased in between model-years 2009 and 2016, and by model-year 2016, would require reductions of tailpipe greenhouse gas emissions from new motor vehicles of approximately 30 percent. California and 16 other states are poised to adopt the standards, assuming the federal EPA grants California’s waiver request and barring any additional legal challenges.
Map of States with Greenhouse Gas Vehicle Standards