On May 16, the US Court of Appeals for the District of Columbia Circuit announced that it was delaying scheduled June 2 oral arguments before a three-judge panel in litigation over the Clean Power Plan. Instead, the DC Circuit will hear oral arguments in the litigation before all participating judges on September 27. The Clean Power Plan, the centerpiece of the Obama administration's efforts to reduce greenhouse gas emissions, would establish Clean Air Act Section 111(d) standards for CO2 emissions from the existing power plants.

The unusual order by the DC Circuit could have several implications for the ultimate legal fate of the Clean Power Plan. First, the en banc review by the DC Circuit would seem to favor EPA given that seven out of the 11 active justices were appointed by Democratic presidents. DC Circuit Judge Merrick Garland, however, is not considering cases while his nomination to the US Supreme Court remains pending (Garland was nominated to the DC Circuit by President Bill Clinton). Judge Nina Pillard, who President Obama nominated to the DC Circuit, did not participate in the court's decision for an en banc review of the Clean Power Plan, though it is unclear whether she will recuse herself from the oral arguments. Even if both Garland and Pillard were to recuse themselves from the Clean Power Plan litigation, there would still be five Democratic-appointed judges to four Republican-appointed judges. However, it is unclear how the court would decide this case in light of its complicated constitutional and statutory issues and the unusual course this case has already taken.

Second, the DC Circuit's announcement may expedite the US Supreme Court's consideration of the Clean Power Plan. With the initial three-judge panel, the losing party was potentially expected to request a full en banc hearing by the DC Circuit, adding another layer of judicial review before the case would be considered by the US Supreme Court. Now with the en banc hearing occurring in September, it is more likely that the US Supreme Court could consider the legality of the Clean Power Plan earlier, potentially in 2017.

Finally, the DC Circuit's announcement means that it is highly unlikely for the court to issue a decision on the Clean Power Plan until after the November presidential and congressional elections. The results of the presidential election may determine the fate of the Clean Power Plan, considering the ideological differences over climate change between presumptive Republican nominee Donald Trump and presumptive Democratic nominee Hillary Clinton. The next president may also be left with the task of filling the current vacancy on the US Supreme Court, and that judge could be the deciding vote on whether to uphold the Clean Power Plan.

In February, just days before Justice Antonin Scalia's death, the US Supreme Court issued a stay on the Clean Power Plan, with all five conservative judges supporting the stay and the four liberal judges opposing it. It is worth noting that the stay is not a judgment on the merits of the case, and it remains to be seen how the justices would rule once the Clean Power Plan litigation is before the court. Notably, Justice Anthony Kennedy, who supported the stay and who is often considered a swing vote, sided with the liberal judges in the 2007 EPA v. Massachusetts case in which the Supreme Court held that EPA has the authority to regulate greenhouse gas emissions.

Courts will need to resolve statutory, constitutional and procedural issues in assessing the legality of the Clean Power Plan. Arguably the most high-profile argument against the Clean Power Plan is whether EPA exceeded its statutory authority under the Clean Air Act in setting CO2 standards that relied on "beyond the fence line" measures (e.g., increased generation from natural gas and renewables). State and industry petitioners contend that the Clean Air Act only allows EPA to regulate emission-reduction activities at the actual power plant (e.g., efficiency improvements), but not other activities, such as increased generation from natural gas and renewables. EPA’s brief, however, argues that Section 111(d) of the Clean Air Act provides the agency with the authority to target “generation-shifting measures.” In its brief to the DC Circuit, EPA points to other Clean Air Act rules, including those issued under Section 111(d), that have relied on “generation-shifting” measures to meet emission reduction targets.

Other key legal issues in the case include whether the 1990 Clean Air Act amendments preclude EPA from regulating CO2 emissions under Section 111(d), and whether the Clean Power Plan represents an unconstitutional intrusion on states’ rights. Alleged procedural defects with the Clean Power Plan will also be considered.