MT Const., Article I, Section 8

Amendment by legislative referendum. Amendments to this constitution may be proposed by any member of the legislature. If adopted by an affirmative roll call vote of two-thirds of all the members thereof, whether one or more bodies, the proposed amendment shall be submitted to the qualified electors at the next general election. If approved by a majority of the electors voting thereon, the amendment shall become a part of this constitution on the first day of July after certification of the election returns unless the amendment provides otherwise.