— The Supreme Court handed the Obama administration a significant victory on an environmental issue, with a 6-2 decision that upholds a regulation requiring Midwestern states with coal-fired power plants to reduce harmful emissions that drift to the East Coast and mid-Atlantic.
Tuesday's ruling could end a standoff among the states over pollution control that has lasted since the 1990s.
The Environmental Protection Agency's "cross-state air pollution rule" covers the 28 states in the eastern half of the nation and would affect 240 million Americans.
When the EPA announced the current version of the rule in 2011, agency officials estimated that pollution carried downwind from coal-fired plants was triggering more than 400,000 asthma attacks a year and causing 34,000 premature deaths.
The question of who should pay to clean up that pollution has pitted Eastern states, which receive most of emissions, against states farther west that generate it. The regulation also has a major effect on the coal and utility industries because efforts to curtail pollution are likely to further reduce the use of coal in power generation.
Environmentalists, leaders of several Eastern states and public health groups cheered the decision.
"Millions of Americans will breathe easier, thanks to the decision today," the American Lung Assn. said. EPA Administrator Gina McCarthy called the ruling "a big win for the nation's public health and a proud day for the agency."
But a spokesperson for some of the affected industries decried the ruling.
"EPA continues to abuse the Clean Air Act, imposing overreaching regulations that promise little gain with great pain for American consumers and the broader American economy," said Laura Sheehan, spokeswoman for the American Coalition for Clean Coal Electricity.
Under the Clean Air Act, states and the EPA are supposed to work together to reduce smog. Eastern states have long complained that they could not meet their targets because of pollution that drifts in from their neighbors.
In 1990, Congress amended the Clean Air Act to strengthen the EPA's authority to deal with that problem, but the agency's efforts to do so have generated years of litigation and political battles.
EPA's latest version of its regulation, announced in 2011, required upwind states to install technology to cut harmful emissions, including those that contribute to smog. Texas and several Midwestern states joined electric utility companies in suing to block the rule. Two years ago they won a victory in the U.S. Court of Appeals for the District of Columbia, which said the EPA had gone too far.
But the Supreme Court disagreed and revived the rule Tuesday in an opinion written by Justice Ruth Bader Ginsburg and joined by Chief Justice John G. Roberts Jr. and Justices Anthony M. Kennedy, Stephen G. Breyer, Sonia Sotomayor and Elena Kagan.
Ginsburg said the EPA's regulation, which takes into account costs and how much each state already has done to clean up its pollution, was a reasonable means of enforcing the Clean Air Act.
"Left unregulated, the emitting upwind state will reap the benefits of economic activity causing the pollution without bearing the full costs of emissions generated from that state," Ginsburg wrote. "Conversely, downwind states to which the pollution travels are unable to achieve clean air because of the influx of out-of-state pollution they lack the ability to control."
Solving the problem is a "complex challenge" because "regulators must account for the vagaries of the wind," Ginsburg wrote.
Justices Antonin Scalia and Clarence Thomas dissented, while Justice Samuel A. Alito Jr. took no part in the case. In Scalia's dissent, part of which he read from the bench, he said the court majority had given regulators too much free rein and trampled on the rights of the affected states.
Although the Supreme Court ruling validated the EPA's authority to cut power plant pollution, it is "not a panacea" for pollution-induced public health problems, warned S. William Becker, executive director of the National Assn. of Clean Air Agencies, a coalition of state regulators.
The rule calls for reduction of ozone to 84 parts per billion, Becker said. But the EPA already is in the process of lowering that allowable level of pollution to further protect public health. Over the next two years the agency is expected to adopt a standard between 60 and 70 parts per billion.
"The environmentalists are cheering, and there's a lot to cheer in the rule," Becker said. "But my only asterisk is that it's not time to celebrate too early because we need to get emissions down to the newer ozone standards."