Mont. Code Ann. § 32-1-471

Any officer or employee of any bank 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 bank as collateral, for safekeeping or in any other manner, and to which the bank has not acquired full title, is guilty of theft and upon conviction shall be punished as for other felonies.