7 U.S. Code § 6809 - Investigations and power to subpoena
The Secretary may make such investigations as the Secretary considers necessary for the effective administration of this chapter, or to determine whether any person has engaged or is engaging in any act that constitutes a violation of this chapter or any order or regulation issued under this chapter.
For the purpose of an administrative hearing held under section 6807(a)(2) or 6808(c)(3) of this title, the presiding officer may 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 the records may be required from any place in the United States.
In the case of contumacy by, or refusal to obey a subpoena issued under subsection (b) 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 conducted, or where the person resides or conducts business, in order to enforce a subpoena issued under subsection (b).
Any failure to obey the order of the court may be punished by the court as a contempt of court.
Process in any proceeding under this subsection may be served in the United States judicial district in which the person being proceeded against resides or conducts business or wherever the person may be found.