Mo. Rev. Stat. § 41.490
The governor shall have the power to organize from the unorganized militia of Missouri a state defense force for duty within or without the state to supplement the Missouri National Guard or replace it when it is mobilized in federal service. The Missouri state defense force may be used to execute the laws, suppress insurrections, repel invasion, suppress lawlessness, and provide emergency relief to distressed areas in the event of earthquake, flood, tornado, or actual or threatened enemy attack or public catastrophe creating conditions of distress or hazard to public health and safety beyond the capacity of local or established agencies. The force shall consist of such organized troops, auxiliary troops, staff corps and departments as the governor deems necessary. The governor shall prescribe the strength and composition of the various units of the same, uniform and insignia and the qualifications of its members, and shall have the power to grant a discharge therefrom for any reason deemed by him sufficient.
§ 41.490, RSMo