E. Scott Pruitt, President-elect Donald Trump’s pick to lead the Environmental Protection Agency, is a chief foe of the agency who could unravel two of the Obama administration’s signature regulations: the Clean Power Plan and the Waters of the United States rule.

Both rules are litigation targets from companies and dozens of states, including Oklahoma, that are fighting now in federal appeals courts. The resolution of the cases—especially any action in the U.S. Supreme Court—would spill into Trump’s administration.