A federal judge has disqualified the Keller Lenkner law firm from handling a lawsuit against Uber due to one of the firm’s lawyers work alongside the ride-hailing giant as the top appellate counsel at the U.S. Chamber of Commerce. Warren Postman, who left the U.S. Chamber Litigation Center to join Keller Lenkner as a partner last summer, represented the Chamber as a co-plaintiff alongside Uber in a lawsuit challenging a Seattle ordinance that authorized independent contractor drivers to collectively bargain. Lawyers at Keller Lenkner had argued Postman never represented Uber as a client, and that he never accessed privileged or confidential Uber information relevant to the case the firm was pursuing on behalf of Studio City-based Diva Limousine Ltd. The livery cab company alleged Uber’s classification of its drivers as contractors, rather than employees, violated California labor law and allowed Uber to compete unfairly. But in a ruling issued Wednesday ( THE OFFICIAL COURT DOCUMENT ), U.S. District Judge Edward Chen of the Northern District of California found that Postman’s work on the Seattle case was “extensive” and that there was a substantial relationship between the Seattle case and the one he was pursuing on behalf of Diva. “The receipt of confidential information is presumed where there is a substantial relationship between two representations,” Chen wrote. “Where an attorney successively represents clients with adverse interests, his disqualification is required under the California Rules of Professional Conduct if ‘the subjects of the two representations are substantially related.’” Chen noted Keller Lenkner and Postman had consulted with independent ethics experts who had opined the lawyer’s prior work for the Chamber did not appear to create a conflict. But the judge wrote the firm couldn’t point to a case where seeking out such an opinion had protected a firm from disqualification. “While it may have been prudent for Mr. Postman and KL to seek an ethics consultation before undertaking to represent Diva, unilaterally obtained ethics guidance is not a shield that allows counsel to continue a representation where that representation creates an untenable conflict,” Chen wrote. Neither Postman nor name partners Ashley Keller and Travis Lenker immediately responded to emails seeking comment Wednesday. Uber representatives declined to comment. The company is represented in the case by lawyers at Morgan, Lewis & Bockius.