On April 5, the U.S. Court of Appeals for the D.C. Circuit vacated a Trump-era rule that would have prevented the Environmental Protection Agency (EPA) from setting greenhouse gas (GHG) emissions standards for almost any class of stationary sources, except for fossil fuel-fired electric generating units. The court’s decision, issued at the request of the new Biden EPA, clears the way for new sector-by-sector GHG regulations should the new administration seek to set new GHG standards under Section 111 of the Clean Air Act (CAA).