7 U.S. Code § 7469 - Investigations and power to subpoena
(a) In general
The Secretary may make such investigations as the Secretary considers necessary—
(1) for the effective carrying out of the responsibilities of the Secretary under this subchapter; or
(b) Power to subpoena
For the purpose of an investigation made under subsection (a) of this section, the Secretary may administer oaths and affirmations and may issue subpoenas to require the production of any records that are relevant to the inquiry. The production of any such records may be required from any place in the United States.
(2) Administrative hearings
For the purpose of an administrative hearing held under section 7467 or 7468 of this title, the presiding officer is authorized to administer oaths and affirmations, subpoena witnesses, compel the attendance of witnesses, take evidence, and require the production of any records that are relevant to the inquiry. The attendance of witnesses and the production of any such records may be required from any place in the United States.
(c) Aid of courts
In the case of contumacy by, or refusal to obey a subpoena to, any person, the Secretary may invoke the aid of any court of the United States within the jurisdiction of which the investigation or proceeding is carried on, or where the person resides or carries on business, to enforce a subpoena issued by the Secretary under subsection (b) of this section. The court may issue an order requiring the person to comply with the subpoena.
Any failure to obey the order of the court may be punished by the court as a contempt of the court.
Process in any such case may be served in the judicial district in which the person resides or carries on business or wherever the person may be found.