WASHINGTON – The U.S. Supreme Court on Tuesday handed the Obama administration an important victory in its effort to reduce power plant pollution in 28 Midwestern and Appalachian states that blows downwind and leads to unhealthy air in states like New York.

The decision caps a decades-long effort by the Environmental Protection Agency to find a legally acceptable way to ensure that states are good neighbors and don’t contribute to pollution problems in downwind states, where environmental officials can do nothing to control it. The rule upheld Tuesday was EPA’s third attempt to solve the problem.