Court Blocks E.P.A. Rule on Cross-State Pollution by CO2, SO2, & NO

The agency was trying to address a problem that has vexed the air pollution control system for at least three decades: how to deal with states whose own air meets standards but whose power plants, refineries and other industrial plants emit sulfur dioxide and nitrogen oxide pollutants that — wind-aided — prevent neighboring states from attaining the level of cleanliness required under federal law.

In a 2-to-1 ruling, a panel of the United States Court of Appeals for the District of Columbia said the E.P.A. had exceeded its authority in the way it apportioned the cleanup work among 28 upwind states.