Andrew Weissmann, the former director of the federal government’s Enron task force, has left his post as cochair of Jenner & Block’s white-collar defense and investigations practice to become the Federal Bureau of Investigation’s new general counsel.

The 53-year-old Weissmann, a New York–based Jenner partner who joined the firm in 2006 and was a member of its management committee, filed notices in several of his cases last week stating that Sunday would be his last day at the firm. A spokesman at the FBI confirmed Weissmann’s hiring.