Mo. Rev. Stat. § 476.550: Not eligible for benefits while retired under other plan.

Any person retiring from office under the provisions of Section 27 of Article V of the Constitution of Missouri shall not be eligible for retirement compensation under sections 476.515 to 476.570 during the period of his compensation under such constitutional provisions, but upon the completion of such period he shall become eligible for retirement compensation under sections 476.515 to 476.570 if he be otherwise qualified as to age and length of service.