7 U.S.C. § 7469: Investigations and power to subpoena

for the effective carrying out of the responsibilities of the Secretary under this subchapter; or to determine whether a person subject to this subchapter has engaged or is engaging in any act that constitutes a violation of this subchapter, or any order, rule, or regulation issued under this subchapter. For the purpose of an investigation made under subsection (a), 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. 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. 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). 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. The site of any hearing held under section 7467 or 7468 of this title shall be in the judicial district where the person affected by the hearing resides or has a principal place of business.