Heath Tarbert, former chairman of the Commodity Futures Trading Commission (CFTC), has been named chief legal officer at Citadel Securities.

Tarbert stepped down as chair of the CFTC in January, a position he held since 2019, but had remained on as a commissioner until recently. His term on the CFTC ran through April 2024. Commissioner Rostin Behnam has served as acting chair of the agency since Tarbert vacated the post.

“Citadel Securities has been a leading advocate for open and transparent markets. I look forward to working with its outstanding team to build upon the firm’s track record of creating better markets for investors,” Tarbert said in a statement released by Citadel. Tarbert will join the company April 5.

Citadel, a Chicago-based trading operation founded by billionaire Ken Griffin, faced a grilling in Congress in February for its role in the GameStop market volatility, along with retail brokerage Robinhood. Lawmakers focused on a practice known as payment for order flow, through which Citadel and other trading operations pay brokerages like Robinhood to execute orders.

When Robinhood was forced to pause trading in GameStop and several other stocks in late January because the heavy trading by its users left the company unable to meet its margin requirements, some market watchers said Citadel might have been the main beneficiary of the pause. Citadel has said it was not involved in Robinhood’s trading pause “in any way.”

With Tarbert gone, President Joe Biden will have two CFTC commissioner slots to fill. The other is currently held by Republican Brian Quintenz, whose term expired last year. No more than three of the five commissioners at any one time may be from the same political party.

Tarbert will replace Citadel General Counsel Steve Luparello, himself a former regulator with the Securities and Exchange Commission, who is scheduled to retire at the end of the year, Bloomberg reported.