in one of the most significant of environment cases, on April 2, 2007, the us Supreme Court ruled that the country's environment agency had the authority and responsibility to regulate carbon dioxide emissions and other greenhouse gases (ghgs) under the Clean Air Act, 1963, as an "air pollutant'.

The court was hearing the Massachusetts et al vs Environment Protection Agency (epa) et al case filed against epa by Massachusetts and 11 other states, and environmental groups and others in 1999 petitioning epa to set carbon dioxide emissions standards (see