The head of enforcement at the U.S. Commodity Futures Trading Commission is leaving the regulator to return to private practice.

Gregory Mocek, who has served as director of enforcement since 2002 and under whose tenure the CFTC began its probe into trading at collapsed hedge fund Amaranth Advisors, will step down within 60 days. He is set to join law firm McDermott Will & Emery in its energy and derivatives markets practice.

He is to be succeeded on an interim basis by Stephen Obie, the CFTC’s regional counsel in New York.

“Leading a division of professionals who are considered to be the best in the world at investigating and litigating commodity fraud and manipulation was an honor,” Mocek said.