Opponents of the CPP, including states, industry, and the Chamber of Commerce, challenged the rule in the United States Court of Appeals for the D.C. Circuit. Among other things, they argued that, under their reading of the Clean Air Act (CAA), the EPA’s decision to regulate hazardous pollutants emitted from power plants deprived it of the authority to regulate CO2 emissions from those same power plants. Republican members of Congress filed a friend-of-the-court brief in support of the rule’s challengers, arguing that the rule usurps Congress’s ability to make policy for the nation.

CAC filed a friend-of-the-court brief in the consolidated CPP cases on behalf of current members of Congress and bipartisan former members of Congress who were familiar with the CAA and were either sponsors of CAA legislation, participants in drafting the 1990 CAA amendments, or served on key committees with jurisdiction over the EPA and CAA. Our brief on behalf of these current and former members of Congress argued that the rule’s challengers fundamentally misunderstood the CAA and the authority it conferred on the EPA. As our brief demonstrated, the CAA gave EPA, as the delegated expert agency, discretion to elaborate on criteria set out in the statute, to resolve ambiguities in them, and to apply them to specific new problems as they arose. Congress also intentionally drafted certain provisions with broad language so EPA could play a key role in shaping the approach to developing and setting standards for specific sources and pollutants, both known and unknown.

By promulgating rules that were consistent with the CAA’s text, structure, and history (as the CPP was), the EPA conformed to clear congressional instructions and facilitated Congress’s ability to enact a robust clean air and public health policy for the nation. In other words, as we argued in our brief, the Clean Power Plan rule does not “usurp the role of Congress to establish climate and energy policy for the nation,” as conservative members of Congress claimed; rather, it facilitated Congress’s ability to set policy for the nation by implementing the policy objectives Congress enacted in the CAA.

In March 2017, President Trump signed an Executive Order that, among other things, instructed the EPA to reexamine the CPP and “if appropriate . . . publish for notice and comment proposed rules suspending, revising, or rescinding” it.  That same day, the EPA filed a motion with the D.C. Circuit asking that the cases be held in abeyance in light of the agency’s plan to reexamine the rule at issue, and the court granted the EPA’s motion. In June 2019, the Trump administration replaced the CPP with its own rule, and on September 17, 2019, the D.C. Circuit dismissed the petitions as moot.