When the Labor Department brought the fiduciary rule back from the dead in the final year of the Obama presidency, reviving a controversial proposal the agency had tabled in 2011, Gibson, Dunn & Crutcher partner Eugene Scalia considered it a privilege to challenge the retirement-savings regulation.

For the industry, the rule threatened to usher in some of the most sweeping regulatory changes in 50 years. For Scalia, co-chairman of Gibson Dunn’s administrative law and regulatory practice group, it represented “one of the broadest, most aggressive regulatory maneuvers I’ve ever seen by an agency,” he said.