Mont. Code Ann. § 70-20-306

Lineal and collateral warrants, with all their incidents, are abolished, but the heirs and devisees of every person who has made any covenant or agreement in reference to the title of, in, or to any real property are, except as provided in 70-1-522, answerable upon the covenant or agreement to the extent of the land descended or devised to them in the cases and in the manner prescribed by law.