(Reuters) - Citadel Securities has appointed Heath Tarbert as chief legal officer, the electronic trading firm said on Thursday, months after he resigned as chair of the Commodity Futures Trading Commission (CFTC). The company, co-founded by billionaire investor Kenneth Griffin, said Tarbert would take on his new role on Monday and be responsible for all legal and compliance matters at the company. Tarbert, a former corporate attorney and senior Treasury Department official, stepped down as CFTC chair in January. He was nominated by former President Donald Trump to be both chair and one of five commissioners at the CFTC, taking office in July 2019. His appointment comes as Citadel Securities gets embroiled in January’s GameStop saga that put a spotlight on the huge role the company plays in the U.S. retail trading market, accounting for around 40% of executed retail trades. Citadel Securities, led by Peng Zhao, competes with other market makers for order flow from companies, including Robinhood, and receives a large percentage of orders based on execution quality.