On Sept 12, 2007 a federal judge in Vermont ruled that the Environmental Protection Agency (EPA) has an obligation to regulate carbon dioxide under the Clean Air Act.
The U.S. Supreme Court ruled on April 2, 2007 in Massachusetts vs Environmental Protection Agency (EPA) that the agency does have the authority to regulate carbon dioxide as a criteria pollutant under the Clean Air Act. More specifically, the court to ruled 5 to 4 that the EPA violated the Clean Air Act by improperly declining to regulate new-vehicle emissions standards to control carbon dioxide, which contributes to global warming. Background: when groups in Massachusetts petitioned the EPA to set standards for greenhouse gas emissions for new vehicles EPA declined in 2003 citing "numerous areas of scientific uncertainty" about the causes and effects of global warming. Massachusetts, along with other states and cities, took the agency to court.
The U.S. Supreme Court also unanimously ruled on April 2, 2007 in Environmental Defense vs Duke Energy Corporation that industrial smokestacks and power plants must meet the Clean Air Act's New Source Review program (NSR), which requires that when large industrial facilities, such as power plants, refineries and chemical plants, expand operations and increase air pollution, they must also modernize air pollution controls.