Mo. Rev. Stat. § 104.271

Notwithstanding any other provision of law to the contrary, a member of the Missouri transportation department and highway patrol retirement system or a member of the Missouri state employees' retirement system shall be entitled to retire with a normal annuity and shall be entitled to elect any of the survivor benefit options and shall also be entitled to any other provisions of this chapter that relate to retirement with a normal annuity if the sum of the member's age and creditable service equals eighty years or more and if the member is at least forty-eight years of age.