7 U.S.C. § 4610a

(a) In general The Secretary may make such investigations as the Secretary determines necessary— (1) for the effective administration of this chapter; or (2) to determine whether a person has engaged or is engaging in any act or practice that constitutes a violation of any provision of this chapter, or of any order, rule, or regulation issued under this chapter. (b) Power to subpoena (1) Investigations For the purpose of an investigation made under subsection (a), the Secretary is authorized to administer oaths and affirmations and to issue a subpoena 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 4609 or 4610 of this title, the presiding officer is authorized to administer oaths and affirmations, subpoena witnesses, compel their attendance, take evidence, and require the production of any records that are relevant to the inquiry. Such 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 case of contumacy by, or refusal to obey a subpoena issued to, any person, the Secretary may invoke the aid of any court of the United States within the jurisdiction of which such investigation or proceeding is carried on, or where such person resides or carries on business, in order to enforce a subpoena issued by the Secretary under subsection (b). The court may issue an order requiring such person to comply with such a subpoena. (d) Contempt Any failure to obey such order of the court may be punished by such court as a contempt thereof. (e) Process Process in any such case may be served in the judicial district in which such person resides or conducts business or wherever such person may be found. (f) Hearing site The site of any hearings held under section 4609 or 4610 of this title shall be within the judicial district where such person resides or has a principal place of business.