Any other provision of this article to the contrary notwithstanding, any person who first becomes an employee of an employer at age 60 or later may elect not to become a member of this retirement system. Such election shall be made in writing to the board within 30 days of first becoming an employee of an employer; otherwise, the person shall become a member of this retirement system. The election provided for in this subsection shall be irrevocable.
OCGA § 47-2-72