The U.S. Supreme Court said Tuesday it won’t review a lower court ruling concerning the Environmental Protection Agency’s (EPA) regulation of greenhouse gas (GHG) emissions from many existing power plants.

The case stems from a June 2014 Supreme Court decision in which justices affirmed in part and reversed in part a U.S. Court of Appeals for the District of Columbia Circuit decision upholding EPA regulation of GHG emissions under the Clean Air Act’s (CAA) Prevention of Significant Deterioration program [Utility Air Regulatory Group v. EPA, 134 S. Ct. 2427 (2014)] (see Daily GPI, June 23, 2014).

The justices said EPA lacked authority in some cases to force companies to evaluate ways to reduce carbon dioxide (CO2) emissions, a rule that is used in permitting expansions or new facilities that may increase CO2 emissions.

Not affected by the high court’s ruling were some EPA proposals for new and existing power plants that would require, among other things, a 30% reduction in GHG emissions by 2030 (see Daily GPI, June 2, 2014). Also preserved was EPA’s authority over facilities’ emissions that already were regulated, other than GHG.

On remand from the Supreme Court, the appeals court applied the ruling exactly as the higher court had directed, “acting as if the Supreme Court had only reversed [the lower court decision] and did not, in fact, affirm a significant part of that decision,” according to a coalition of environmental groups that filed for rehearing of the case. On Tuesday, the Supreme Court denied the petition.

EPA was accused of overreach in 2010 when the final GHG rules were issued (see Daily GPI, March 30, 2010). The rules require stationary sources to obtain CAA permits covering GHGs after January 2011. The agency said at the time it had pledged to take sensible steps to address the billions of tons of GHG pollution that it said threatened health and welfare. However, it wanted to provide time for large facilities and regulators to put in place cost-effective, innovative technologies to reduce CO2 pollution.