The Supreme Court curbed the Environmental Protection Agency's ability to broadly regulate carbon emissions from existing power plants.
The ruling was 6-3. Chief Justice John Roberts wrote the opinion for the conservative majority, with the three liberal justices dissenting.
Roberts said that "our precedent counsels skepticism toward EPA's claim" that the law "empowers it to devise carbon emissions caps based on a generation shifting approach."
"Under our precedents, this is a major questions case," Roberts wrote, adding that "there is little reason to think Congress assigned such decisions to the Agency."
Roberts wrote that capping carbon dioxide emissions at a level that will force a nationwide transition away from the use of coal may be a "sensible" solution.
"But it is not plausible that Congress gave EPA the authority to adopt on its own such a regulatory scheme" under the law in question.
"A decision of such magnitude and consequence rests with Congress itself, or an agency acting pursuant to a clear delegation from that representative body," he wrote.