Mont. Code Ann. § 32-2-937

An officer or employee of a mutual association doing business in this state who, except in the manner authorized by law or the contract of the parties, pledges or in any way alienates any notes, stocks, bonds, mortgages, securities, or any other property coming into the officer's or employee's hands or into the possession of the mutual association as collateral, for safekeeping or in any other manner, and to which the mutual association has not acquitted full title, is guilty of theft and upon conviction must be punished as for other felonies.