Mo. Rev. Stat. § 306.167: Powers of peace officer when working in cooperation with other law enforcement agency.

The uniformed members of the water patrol division, with the exception of radio personnel, shall have full power and authority as now or hereafter vested by law in peace officers when working with and at the special request of the sheriff of any county, the chief park ranger of any first class county not having a charter form of government and containing a portion of a city with a population exceeding four hundred thousand inhabitants, the chief of police of any city, or the superintendent of the state highway patrol; provided, however, that such power and authority shall be exercised only upon the prior notification of the chief law enforcement officer of each jurisdiction.