The U.S. Supreme Court last week set limits on EPA’s ability to regulate emissions of carbon dioxide and other greenhouse gases from power plants, chemical manufacturing facilities, and petroleum refineries. The decision addresses a part of the Clean Air Act that requires companies to obtain permits when they build a new plant or modify an existing facility in ways that will increase emissions. In a5-4 ruling, the high court says EPA cannot require industrial sources of pollution to obtain permits strictly on the basis of their potential greenhouse gas emissions. But the situation is different if permits are also needed because the new or modified facility will emit other pollutants, such as nitrogen oxides or sulfur dioxide, the Court says. Under this condition, the agency can require installation of the “best available” pollution-control technology to limit all types of regulated emissions, including greenhouse gases.