5 U.S.C. § 304 — Subpenas

(a) The head of an Executive department or military department, or a bureau within one of those, that has a claim against the United States pending, can apply to a judge or clerk of a U.S. court to issue a subpoena for a witness within that court's jurisdiction. The subpoena orders the witness to appear at a stated time and place before someone authorized to take depositions to be used in U.S. courts. There, the witness must give full and true answers to written questions and follow-up questions submitted with the application, or be examined and cross-examined out loud about the claim. (b) If a witness who has been served with the subpoena neglects or refuses to appear, or appears but refuses to testify, the judge of the district where the subpoena was issued may, through proper legal process, act to enforce obedience to the subpoena, or to punish the witness for disobeying it — the same way a U.S. court could act in the case of a subpoena ad testificandum (a subpoena to testify) that the court itself issued.