The Supreme Court agreed Friday to hear a set of cases challenging the Environmental Protection Agency’s authority to regulate greenhouse gases, potentially limiting the Biden administration’s options to curb planet-heating pollution.

The lawsuits, filed by Republican-controlled states and a West Virginia oil company, aim to curb the federal government’s power to mandate a transition away from fossil-fueled power plants.

If the high court’s 6-3 conservative majority finds in favor of the plaintiffs, the ruling wouldn’t eliminate the federal government’s ability to regulate carbon dioxide emissions under the Clean Air Act, a legal determination known as the endangerment finding. It would, however, restrict the legal routes through the Clean Air Act for enacting such rules. That could make it harder for the United States to hit its goal to cut emissions in half by the end of this decade.