Mont. Code Ann. § 16-10-205

In establishing the cost of cigarettes to the retailer or wholesaler, the invoice cost of said cigarettes purchased at a forced, bankrupt, or closeout sale or other sale outside of the ordinary channels of trade may not be used as a basis for justifying a price lower than one based upon the replacement cost of the cigarettes to the retailer or wholesaler in the quantity last purchased through the ordinary channels of trade.