Yesterday, the D.C. Circuit Court of Appeals issued a decision in EME Homer City Generation, L.P. v. EPA that rejects the U.S. Environmental Protection Agency’s approach to regulating upwind pollution from coal- and natural gas-fired power plants, among other sources. The so-called Transport Rule, also known as the Cross-State Air Pollution Rule, had sought to define emissions reduction responsibilities for Texas and 27 eastern states based on those states’ contributions to downwind states’ air quality problems. The Rule would have imposed caps on sulfur dioxide and nitrogen oxide emissions.

In a 2-1 ruling, the D.C. Circuit found that the Transport Rule exceeds EPA’s statutory authority. The Court ordered EPA to continue to enforce a 2005 regulation know as the Clean Air Interstate Rule until it established a lawful replacement to the Transport Rule. That process is widely expected to take years to accomplish.

One of the immediate consequences of the ruling is likely a stay of execution for certain older coal-fired power plants. Under the Transport Rule, owners of such plants would either have had to close their facilities or install expensive pollution control equipment.