(1) Subject to a member's right to a refund of the member's accumulated contributions under Title 19, chapter 2, part 6, a member is eligible for a nonforfeitable service retirement benefit under 19-9-804 after terminating service if:
(a) the member has completed 20 years or more of membership service; or
(b) the member is vested and has reached 50 years of age.
(2) For purposes of compliance with section 411 of the Internal Revenue Code, 26 U.S.C. 411, a member described in subsection (1)(b) is treated as having attained normal retirement age and has a nonforfeitable right to the member's service retirement.