Mo. Rev. Stat. § 334.1700: Member states, effective date and amendment.

1. Any state is eligible to become a member of the Compact.

*2. The Compact shall become effective and binding upon legislative enactment of the Compact into law by no less than seven (7) states. Thereafter, it shall become effective and binding on a state upon enactment of the Compact into law by that state.

3. The governors of non-member states, or their designees, shall be invited to participate in the activities of the Interstate Commission on a non-voting basis prior to adoption of the Compact by all states.

4. The Interstate Commission may propose amendments to the Compact for enactment by the member states. No amendment shall become effective and binding upon the Interstate Commission and the member states unless and until it is enacted into law by unanimous consent of the member states.