A federal judge in San Francisco on Thursday disqualified lawyers at Quinn Emanuel Urquhart & Sullivan from representing defunct ride-hailing service Sidecar in an antitrust lawsuit against the law firm’s former client Uber Technologies Inc.

U.S. Chief Magistrate Judge Joseph Spero found that the firm’s work defending Uber from predatory pricing claims brought in a 2014 lawsuit from a Maryland taxi company had a “substantial relationship” to the case the firm’s lawyers were pursuing on behalf of Sidecar.