Mo. Rev. Stat. § 41.060: Militia service, persons exempt.

The following persons shall be exempt from militia service:

(1) Persons exempt from militia service by the laws of the United States;

(2) Regular or duly ordained ministers of religion, or duly elected church officials regularly conducting church services, or those recognized by their church as devoting the major portion of their time to the practice of religion;

(3) Students preparing for the ministry in recognized theological or divinity schools.