By Lawrence Hurley
WASHINGTON, April 29 (Reuters) - The U.S. Supreme Court on Tuesday upheld a major federal regulation requiring certain states to limit air pollution that crosses into neighboring states.
The ruling, on a 6-2 vote with Justice Samuel Alito recused, marks a victory for the environmental agenda of President Barack Obama. The rule in question mostly regulates emissions from coal-fired power plants.
The regulation, which requires 28 states to reduce emissions of sulfur dioxide and nitrogen oxides, was put on hold while courts weighed the challenges.
Among the challengers are Entergy Corp, Luminant Holding Company and the United Mine Workers of America.
Justice Ruth Bader Ginsburg, writing on behalf of the court, said the provision of the Clean Air Act does not require the U.S. Environmental Protection Agency to consider each state's proportionate responsibility for the emissions in question.
Justice Antonin Scalia, joined by Justice Clarence Thomas, wrote a dissenting opinion, saying the EPA had effectively rewritten the Clean Air Act in adopting the regulation.
In striking down the rule in an August 2012 ruling, the U.S. Court of Appeals for the District of Columbia Circuit wrote in part that the EPA could not impose a federal plan on a state until the state was given notice of the amount of pollution it emitted that makes it more difficult for other states, downwind, to meet government-set air quality standards.
The appeals court also found that EPA authority was limited over what factors it could consider when setting targets for the states. The Obama administration appealed the decision to the Supreme Court, which by its ruling on Tuesday reversed the appeals court.
The administration said that the Clean Air Act requirement that the EPA and states limit pollution that will "contribute significantly" to another state's air quality problems is not limited to consideration of the amount of pollution. The agency can also take into account how difficult it is to reach a particular target, government lawyers said.
The two consolidated cases are EPA v. EME Homer City Generation and American Lung Association v. EME Homer City Generation, U.S. Supreme Court, 12-1182 and 11-1183. (Reporting by Lawrence Hurley; Editing by Howard Goller)