Mont. Code Ann. § 81-23-401

Except for the premises of a small dairy as defined in 81-21-101, the department may enter, at all reasonable hours, all places where milk is produced, processed, bottled, handled, or stored or where the books, papers, records, or documents relative to those transactions are kept, and may inspect and copy them in any place in this state. The department may administer oaths and take testimony for the purpose of ascertaining facts which, in the judgment of the department, are necessary to administer this chapter.