7 U.S. Code § 7488 - Investigations and power to subpoena
The Secretary may make such investigations as the Secretary considers necessary—
(b) Oaths, affirmations, and subpoenas
For the purpose of an investigation under subsection (a) of this section, the Secretary 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 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 issued to, any person, the Secretary may request 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, in requiring the attendance and testimony of the person and the production of records.
(2) Enforcement order of the court
The court may issue an enforcement order requiring the person to appear before the Secretary to produce records or to give testimony concerning the matter under investigation.
A failure to obey an enforcement order of the court under paragraph (2) may be punished by the court as a contempt of the court.