7 U.S.C. § 2279f: Subpoena authority

The Secretary concerned shall have power to subpoena the attendance and testimony of any witness, and the production of all documentary evidence relating to the enforcement of section 2279e of this title or any matter under investigation in connection with this section and section 2279e of this title . The attendance of any witness and the production of documentary evidence may be required from any place in the United States at any designated place of hearing. In the case of disobedience to a subpoena by any person, the Secretary concerned may request the Attorney General to invoke the aid of any court of the United States within the jurisdiction in which the investigation is conducted, or where the person resides, is found, transacts business, is licensed to do business, or is incorporated, in requiring the attendance and testimony of any witness and the production of documentary evidence. In case of a refusal to obey a subpoena issued to any person, a court may order the person to appear before the Secretary concerned and give evidence concerning the matter in question or to produce documentary evidence. Any failure to obey the court’s order may be punished by the court as a contempt of the court. Witnesses summoned by the Secretary concerned shall be paid the same fees and mileage that are paid to witnesses in courts of the United States, and witnesses whose depositions are taken, and the persons taking the depositions shall be entitled to the same fees that are paid for similar services in the courts of the United States. The Secretary concerned shall publish procedures for the issuance of subpoenas under this section. Such procedures shall include a requirement that subpoenas be reviewed for legal sufficiency and signed by the Secretary concerned. If the authority to sign a subpoena is delegated, the agency receiving the delegation shall seek review for legal sufficiency outside that agency. Subpoenas for witnesses to attend court in any judicial district or testify or produce evidence at an administrative hearing in any judicial district in any action or proceeding arising under section 2279e of this title may run to any other judicial district.