WASHINGTON - The U.S. Supreme Court handed President Barack Obama a major victory yesterday when it upheld an administration rule that requires steep reductions in power-plant pollutants that are generated in states such as Ohio and settle in other states.

WASHINGTON � The U.S. Supreme Court handed President Barack Obama a major victory yesterday when it upheld an administration rule that requires steep reductions in power-plant pollutants that are generated in states such as Ohio and settle in other states.

In a 6-2 decision, the justices approved a 2011 regulation issued by the U.S. Environmental Protection Agency that had been challenged by Ohio Attorney General Mike DeWine and officials in states in the Midwest and South producing large amounts of sulfur dioxide and nitrogen oxide.

The EPA regulation calls for 27 states � including Ohio � to limit the emissions from coal-fired power plants. Those emissions scatter across the Eastern states, making it difficult for areas without many coal-fired plants to achieve clean-air standards required by the nation�s clean-air laws.

Writing for the majority, Justice Ruth Bader Ginsburg said the �EPA�s cost-effective allocation of emission reductions among� states that produce pollution is �a permissible, workable, and equitable interpretation� of the nation�s clean-air laws.

Joining Ginsburg to form the majority were Chief Justice John Roberts and Justices Anthony Kennedy, Sonia Sotomayor, Elena Kagan and Stephen G. Breyer. Justices Clarence Thomas and Antonin Scalia dissented; Justice Samuel Alito did not take part in the case.

With the ruling, the case returns to a federal appeals panel in Washington, which in 2012 invalidated the EPA rules.

Frank O�Donnell, president of the Washington-based environmental group Clean Air Watch, described the ruling as a �complete vindication of the EPA�s efforts to clamp down on pollution that blows from one state to another.�

Lisa Peterson Hackley, a DeWine spokeswoman, said the ruling gives the federal EPA �the power to dictate any state�s plan for controlling air emissions without giving a state a fair opportunity to put in place its own systems to combat cross-state pollution.�

She added that the decision allows the EPA �to define the standard and also impose its system without first providing the states that opportunity, which we find disappointing.�

It was unclear what the immediate impact would be in Ohio, which is home to American Electric Power, one of the nation�s largest producers of coal-fired electricity.

Melissa McHenry, a spokeswoman for American Electric Power in Columbus, called the decision � disappointing,� but because the justices returned the case to the federal appeals court, �there is no immediate impact on AEP�s operations, and we don�t expect the decision to change our plans for our coal-fueled power generation fleet.�

AEP has about 25 coal-fired power plants. McHenry said the company is expected to spend between $3.5 billion and $4 billion by 2020 to retrofit its plants, � primarily for compliance� with EPA regulations to reduce emissions of mercury.

The 1990 clean-air law signed by President George H.W. Bush helped reduce the amount of pollutants emitted from power plants in the Midwest that settled over the Northeast, causing acid rain.

McHenry said �emissions of sulfur dioxide and nitrogen oxide from AEP�s coal-fueled power plants already have been reduced by more than 80 percent since 1990. Our mercury emissions have declined by nearly 60 percent since 2001, and between 2005 and 2013, AEP reduced its carbon dioxide emissions by 21 percent. AEP will retire nearly 6,600 megawatts for coal-fueled generation between now and 2016.�

jtorry@dispatch.com