The U.S. Department of Justice (DOJ) has filed a series of federal lawsuits against four states—New York, Vermont, Michigan and Hawaii—alleging that recent legislative and enforcement efforts to hold fossil fuel companies financially responsible for climate change unlawfully interfere with federal authority. The lawsuits, filed on April 30 and May 1, challenge two distinct forms of state-led climate action: (1) enacted climate superfund statutes in New York and Vermont, and (2) announced plans by Michigan and Hawaii to bring climate change litigation against fossil fuel companies under state tort law.