WASHINGTON — As ethical questions threaten the Environmental Protection Agency administrator, Scott Pruitt, President Trump has defended him with a persuasive conservative argument: Mr. Pruitt is doing a great job at what he was hired to do, roll back regulations.

But legal experts and White House officials say that in Mr. Pruitt’s haste to undo government rules and in his eagerness to hold high-profile political events promoting his agenda, he has often been less than rigorous in following important procedures, leading to poorly crafted legal efforts that risk being struck down in court.

The result, they say, is that the rollbacks, intended to fulfill one of the president’s central campaign pledges, may ultimately be undercut or reversed.

“In their rush to get things done, they’re failing to dot their i’s and cross their t’s. And they’re starting to stumble over a lot of trip wires,” said Richard Lazarus, a professor of environmental law at Harvard. “They’re producing a lot of short, poorly crafted rulemakings that are not likely to hold up in court.”