In a big victory for the EPA and enviros, a federal appeals court on Friday confirmed the EPA’s authority to make states crack down on power-plant emissions that contribute to dirty air drifting from state to state. Many Northeastern states have long argued that they cannot meet federal air quality standards unless pollution originating in the Midwest is sharply reduced. The EPA responded to these complaints in 1998 by ordering 22 states to make serious cuts to their emissions of nitrogen oxide, a smog-causing chemical released in large quantities by coal-burning power plants. A number of Midwestern states and utilities challenged the EPA’s order, and a U.S. Court of Appeals panel placed the order on hold last year pending further review. With its review complete, the panel ruled on Friday that the EPA can go ahead with its plan. But the case isn’t closed yet — EPA officials expect some states and utilities to appeal.