Lawyers for former pharmaceuticals executive Martin Shkreli have asked a U.S. federal judge for guidance on a demand by lawmakers that Shkreli appear at a hearing on Tuesday, writing that if travel restrictions on him are not lifted, the congressional subpoena should be blocked. Lawyers for Shkreli sent a letter to U.S. District Judge Kiyo Matsumoto in Brooklyn late on Friday laying out the conflict between them and the U.S. House Committee on Oversight and Government Reform over Shkreli’s attendance.