Mont. Code § 16-6-303
It is unlawful for any licensee to sell or keep for sale or have on the licensee's premises for any purpose any liquor except that purchased from an agency liquor store or transferred as allowed in 16-4-404(7). Any licensee found in possession of or selling and keeping for sale any liquor that was not purchased from an agency liquor store or transferred as allowed in 16-4-404(7) shall, upon conviction, be punished by a fine of not less than $500 or more than $1,500, by imprisonment for not less than 3 months or more than 1 year, or by both fine and imprisonment. If the department is satisfied that the liquor was knowingly sold or kept for sale within the licensed premises by the licensee or by the licensee's agents, servants, or employees, the department shall immediately revoke the license.
§ 16-6-303, MCA