The 6 to 3 majority determined in West Virginia et al. v. Environmental Protection Agency that the EPA's "Clean Power Plan" (CPP), promulgated in 2015, overstepped its statutory authority by dictating that power plants must switch from coal to natural gas for generating electricity. The Court ruled that the EPA's powers to limit carbon emissions under the Clean Air Act of 1970 (as amended in 1990) do not include the power to dictate what fuels must be used to produce electricity, a policy known as "generation shifting."

The ruling was based on the Court's "major questions" doctrine, which requires Congress to explicitly spell out in law administrative policy actions that have sweeping "economic and political significance."