Missouri constitution
Article VI: local government
Section 32(b)

In the event of any amendment or revision of the charter of the city of St. Louis which shall reorganize any county office and/or transfer any or all of the duties, powers and functions of any county officer who is then in office, the officer shall serve out the remainder of his or her term, and the amendment or revision of the charter of the city of St. Louis shall take effect, as to such office, upon the expiration of the term of such office holder. In the event of any amendment or revision of the charter of the city of St. Louis which shall reorganize any county office and/or transfer any or all of the duties, powers and functions of any county officer, all of the staff of such office shall be afforded the opportunity to become employees of the city of St. Louis with their individual seniority and compensation unaffected and on such other comparable terms and conditions as may be fair and equitable.