Mo. Rev. Stat. § 105.510
Employees, except police, deputy sheriffs, Missouri state highway patrolmen, Missouri National Guard, all teachers of all Missouri schools, colleges and universities, of any public body shall have the right to form and join labor organizations and to present proposals to any public body relative to salaries and other conditions of employment through the representative of their own choosing. No such employee shall be discharged or discriminated against because of his exercise of such right, nor shall any person or group of persons, directly or indirectly, by intimidation or coercion, compel or attempt to compel any such employee to join or refrain from joining a labor organization, except that the above excepted employees have the right to form benevolent, social, or fraternal associations. Membership in such associations may not be restricted on the basis of race, creed, color, religion or ancestry.
§ 105.510, RSMo