The California Public Employees’ Retirement System asked a U.S. District Court judge in Minneapolis Wednesday to freeze outgoing UnitedHealth Group Chief Executive William McGuire’s $1.1 billion retirement package, pending a lawsuit involving the legality of his stock options.

Calpers is the lead plaintiff named in a shareholder lawsuit against UnitedHealth over its stock-option practices and is asking a to issue a preliminary injunction preventing McGuire from receiving benefits called into question by outside counsel that found evidence of options backdating.

Calpers has also asked that McGuire be prevented from exercising his remaining UnitedHealth stock options and freeze the proceeds he reaped from a Feb. 23 sale of 2.3 million shares of common stock that brought him $136 million.

McGuire’s attorney, David Brodsky, said he was preparing a response to CalPERS’ motion.

“Despite McGuire’s culpable involvement in the backdating scheme and his receipt of millions of backdated stock options, UnitedHealth is poised to allow McGuire to leave the company with a $1.1 billion retirement package,” Calpers said in the court filing.