On September 27, 2016, the U.S. Court of Appeals for the D.C. Circuit heard oral argument in West Virginia v. EPA, the case challenging EPA’s Clean Power Plan. All ten of the active judges on the D.C. Circuit, except for Chief Judge Garland (who has been nominated to the Supreme Court), heard the case. The panel is comprised of six judges appointed by Democratic presidents—including four by President Obama—and four appointed by Republican presidents. The oral argument included a morning session, focusing on EPA’s authority to promulgate the rule, as well as an afternoon session that focused on constitutional claims against the rule.

The challengers to the Clean Power Plan emphasized that the rule, which was issued under § 111(d) of the Clean Air Act, is unlawful because EPA is precluded from regulating power plants under that section because it is already regulating emissions from power plants under § 112 of the Clean Air Act pursuant to the Mercury and Air Toxics Standards (MATS). The judges were not particularly receptive to this argument, although the challengers’ argument that EPA lacks authority to promulgate the rule because Congress has not directly spoken on the matter appeared to get more traction, with Judge Thomas Griffith asking, “why isn't this debate going on in the floor of the Senate?” Other judges, including Judge David Tatel, were receptive to EPA’s argument that it was simply invoking its existing authority, recognized by the Supreme Court in Massachusetts v. EPA, to regulate greenhouse gases under the Clean Air Act.

The court is expected to issue its decision after the November election, although the exact timing is uncertain. The losing party is expected to appeal to the Supreme Court, which typically stops taking cases for review in that term in mid-January. If the D.C. Circuit does not issue its decision until after mid-January 2017, the Supreme Court (if it takes up the case) would not hear oral argument until late 2017, with a decision coming as late as June 2018. The Supreme Court’s stay of the Clean Power Plan will remain in effect until the litigation is resolved. Notwithstanding the stay, many states, including Illinois, New York, and California, are continuing to develop their implementation plans to put into effect if the rule is upheld.