Mont. Code Ann. § 32-1-335

A bank may not purchase or invest its capital or surplus or money of its depositors, or any part of either, in shares of its own capital stock or loan its capital or surplus or the money of its depositors, or any part of either, on shares of its own capital stock unless the purchase or loan is necessary to prevent loss to the bank on debts previously contracted in good faith. However, a bank may redeem or otherwise purchase its own capital stock with the prior approval of the department and subject to any conditions that the department may require.