On April 2, 2008, 12 states, the District of Columbia, two cities, and several environmental groups sued the U.S. Environmental Protection Agency over its failure to regulate greenhouse gas emissions from motor vehicles. The states and other petitioners are asking the U.S. Circuit Court of Appeals for the District of Columbia to force the EPA to issue within 60 days its formal determination of the public health impacts from GHG emissions. In filing their suit, the plaintiffs cited the Supreme Court’s April 2007 decision in Massachusetts et al v. EPA, in which the Court ruled that the EPA is authorized to regulate greenhouse gases under the federal Clean Air Act, and must consider doing so unless it can demonstrate that these gases do not contribute to climate change that harms human health and welfare. Since the Supreme Court’s ruling, the EPA has not issued any formal language or rules for the regulation of CO2 or other greenhouse gases. The states joining the lawsuit include California, Connecticut, Illinois, Maine, Massachusetts, New Jersey, New Mexico, New York, Oregon, Rhode Island, Vermont, Washington, Arizona, Delaware, Iowa, Maryland and Minnesota.