Mont. Code Ann. § 81-8-261

Livestock inspectors, including stock inspectors of a county or district, the sheriff of a county, or a representative of the department of livestock, may enter upon the premises where livestock are being held or sold and must be accorded every facility by the owners of the premises in determining whether a violation of the law is being committed or is likely to be committed. The inspection may not unnecessarily interfere with the conduct of the sales. Livestock sold at the market may not be delivered to the purchaser until the purchaser has first received an inspection certificate issued by one of the officers mentioned in this section, showing clearly and explicitly that the person making the inspection is satisfied as to the ownership of the livestock and the health of all livestock sold.