(a) The governing body of a municipality that began participation in the retirement system before January 1, 1982, by ordinance may provide that persons who hold and are regularly engaged in the performance of duties of an elective office that normally requires actual performance of services in a participating department of the municipality for not less than 1,000 hours a year are employees required to become members of the retirement system.
(b) An ordinance under this section takes effect on the first day of any calendar month after adoption that is designated by the governing body adopting the ordinance.

(c) A person required to become a member under an ordinance adopted under this section becomes a member on the effective date of the ordinance or the date the person takes office, whichever is later, unless the date the person takes office is after the effective date of the ordinance and the person is then ineligible for membership under applicable age restrictions of this subtitle.
(d) A person who becomes a member as provided by this section is entitled to prior service credit as provided by Section 853.302.