Mo. Rev. Stat. § 70.625
In the event an employer acquires employees as the result of acquiring an enterprise from a private business which had an employee retirement plan or from another political subdivision, by agreement with the board after the board has received the advice of its technical advisors concerning such agreement, such employer may provide for coverage under this system of either some part or all of such employee's employment with such private business or other political subdivision, provided such coverage does not duplicate any coverage of a plan similar in purpose to this system which such private business or other political subdivision may have had in effect. In providing for such coverage, an employer and the board shall pursue uniform policies and shall not discriminate in favor of or against any such employee or group of such employees.
§ 70.625, RSMo