The Supreme Court on Monday slightly weakened the Environmental Protection Agency's power to force industrial pollution sources to curb greenhouse-gas emissions as a condition of their Clean Air Act permits.
The decision does not address EPA's recent sweeping proposal to set carbon-emissions standards for power plants, which is a centerpiece of President Obama's second-term climate agenda. Nor does it challenge EPA's underlying authority to regulate heat-trapping emissions.
Instead, the ruling addresses an existing permitting program launched several years ago.
The high court ruled 5-4 that EPA may only require newly built or modified industrial pollution sources—such as power plants, refineries, and factories—to limit greenhouse gases if those same sources must already obtain permits for their so-called conventional pollutants.
In practice, that means only a slight change in the number of big industrial polluters that would be captured by the existing, case-by-case greenhouse-gas permitting program at issue in the case decided Monday. The permitting program itself was not struck down.
The permitting program requires polluters to use so-called best available control technology, which for greenhouse gases has largely meant increased energy efficiency thus far, the Obama administration noted when defending the program before the Court in February.
Limiting the program to facilities that must already get permits for their conventional pollutants (such as emissions that cause smog) addresses the sources of 83 percent of U.S. greenhouse-gas emissions from industrial polluters, compared with 86 percent without that restriction, according to the Obama administration.
"EPA is getting almost everything it wanted in this case," Justice Antonin Scalia said from the bench in announcing the ruling Monday, according to press accounts.
However, there will be plenty of tea-leaf reading about what this portends for the sweeping power-plant standards that EPA is planning to finalize next June, especially about whether conservative justices will take a narrow view of the scope of EPA's discretion in crafting that regulation.
EPA called the ruling a victory.
"The Supreme Court's decision is a win for our efforts to reduce carbon pollution because it allows EPA, states, and other permitting authorities to continue to require carbon-pollution limits in permits for the largest pollution sources," the agency said in a statement.
However, the American Petroleum Institute, one of an array of industry lobbying groups to challenge EPA's permitting rules, saw good news as well.
"It is a stark reminder that the EPA's power is not unlimited," said Harry Ng, the group's general counsel.