A onetime Citadel Investment Group staffer must answer a claim that he violated a non-compete clause when he went into business for himself, an Illinois judge ruled.

Mikhail Malyshev, who used to work in the quantitative trading unit of the Chicago company, set up Teza along with Jace Kohlmeier and attorney Matthew Hinerfeld. But Citadel, the hedge fund run by billionaire Kenneth Griffin, sued in July contending Teza had stolen company-sensitive information from Citadel.

Malyshev, Kohlmeier and Hinerfeld tried to have the lawsuit thrown out of court, but the ruling on Sept. 4 claimed Teza only had to be in existence, rather than actual operation, to be in violation of the agreement with Citadel.

Teza, as a result of the ruling, must file a response to the allegation by Friday.

Legal trouble has dogged Teza from the onset of its formation earlier this year. Goldman Sachs has sued the company claiming a computer expert it hired from the Wall Street firm stole company information.

Citadel has $12 billion under management.