Because both of those rules were finalized under existing laws long before Mr. Obama left office, they cannot be simply undone with a stroke of the president’s pen, legal experts in both the Obama and Trump White Houses have said.
“The executive order has no legal significance at all,” said Richard L. Revesz, a professor of environmental law at New York University. “It’s like the president calling Scott Pruitt and telling him to start the legal proceedings. It does the same thing as a phone call or a tweet. It just signals that the president wants it to happen.”
Still, Mr. Pruitt, who was confirmed by the Senate to his new position this month, is expected to enthusiastically dive in to the lengthy task of undoing major environmental rules on clean water, climate change and air pollution. In his former job as attorney general of Oklahoma, Mr. Pruitt led or took part in 14 lawsuits intended to block the E.P.A.’s major regulations, including the clean water and climate rules that he is now charged with dismantling.
Speaking over the weekend at the Conservative Political Action Conference, Mr. Pruitt told an audience, to applause, “I think there are some regulations that in the near term need to be rolled back in a very aggressive way,” and he said those rollbacks would probably begin this week.
The clean water rule, completed by the Obama administration in spring 2015, was issued under the 1972 Clean Water Act. It gives the federal government broad authority to limit pollution in major bodies of water, like Chesapeake Bay, the Mississippi River and Puget Sound, as well as in streams and wetlands that drain into those larger waters.
Two Supreme Court decisions related to clean water protection, in 2001 and 2006, created legal confusion about whether the federal government had the authority to regulate the smaller streams and headwaters and about other water sources…