On October 29, 2021, the U.S. Supreme Court granted certiorari in West Virginia v. Environmental Protection Agency, a petition filed by several states and coal companies attacking the U.S. Environmental Protection Agency's (EPA’s) regulatory authority under the Clean Air Act (CAA). The Court’s holding in this case would determine EPA’s continued ability to use the CAA—including the national ambient air quality standard (NAAQS) program—as a climate change tool.