Mo. Rev. Stat. § 40.020: Apprehension defined — authority to apprehend, when.

1. "Apprehension" is the taking of a person subject to sections 40.005 to 40.490 into custody.

2. Any person authorized by sections 40.005 to 40.490 or by regulations issued under those sections, to apprehend persons subject to sections 40.005 to 40.490, any marshal of a court-martial appointed pursuant to the provisions of sections 40.005 to 40.490, and any peace officer authorized to do so by law, may do so upon reasonable belief that an offense under sections 40.005 to 40.490 has been committed and that the person apprehended committed it.

3. Commissioned officers, warrant officers, and noncommissioned officers have authority to quell quarrels, frays, and disorders among persons subject to sections 40.005 to 40.490 and to apprehend persons subject to sections 40.005 to 40.490 who take part therein.