Mo. Rev. Stat. § 84.460
So soon as the board created herein shall hold their first meeting, it shall be their duty to inform the chief of police and the other officers of the police force of such city that they require their attendance upon them and obedience to their orders. For failure to attend as required, and for each and every failure to obey the lawful orders of said board, the officers so notified shall be fined in any sum not exceeding five hundred dollars, to be recovered by action at law instituted by said board, in the name of the state. From and after the first meeting aforesaid, the whole of the then existing police force in such city shall pass under the exclusive management and control of the said board, and be subject to no other control and entitled to receive neither orders nor pay, except arrearages then due, from any other authority, and shall so continue, subject, however, to removal or suspension, at the discretion of said board, and with the power in said board to fill vacancies, until said board shall publicly declare that the organization of the police force, created by sections 84.350 to 84.860 is complete. Upon such public declaration, and from the time thereof thenceforward, all ordinances of such city are hereby declared null and void, so far as they conflict with sections 84.350 to 84.860 or assume to confer upon the mayor, chief of police, common council, or any other person or persons, the power to appoint, dismiss, or in any way or to any extent, employ or control any police force organized or to be organized under such ordinances, or any of them, and from and after such public declaration as aforesaid, the police force organized, or which may be organized under such ordinances, or any of them, shall cease to exist, and its functions and powers be at an end.
§ 84.460, RSMo