Mont. Code Ann. § 81-2-101

In the performance of official duties, an agent or officer of the department may enter on or in a lot, yard, land, building, room, premises, enclosure, car, wagon, boat, or other place or vehicle used for the treatment, storage, manufacture, display, or transportation of animals, meat, or dairy products intended for sale or disposal as food. The agent or officer may enter anywhere where livestock may be found that are affected with or that have been exposed to or that the officer has reason to believe are either affected with or have been exposed to an infectious, contagious, communicable, or dangerous disease or disease-carrying insects.