California Code, Government Code - GOV § 21031

(a) “Public service” also means employment by a contracting agency before the effective date of its contract with the board, and is limited to that portion of the service that the agency does not provide in its contract for inclusion as prior service.

(b) A member electing to receive credit for that public service shall make the contributions as specified in Sections 21050 and 21051. The election may be made at any time prior to retirement.

(c) If the contracting agency subsequently amends its contract to include a greater percentage of final compensation as prior service, the electing member shall be refunded that portion of his or her contributions made under this section as represents the additional prior service percentage contracted for by the agency plus interest at the crediting rate.

(d) If the agency pays all or a portion of the normal contributions required to be paid by a member, the contributions required under this section shall be based upon the normal contribution rate that would be applicable to that member if the agency were not paying any normal contributions under Section 20690 or 20691.

(e) This section shall not apply to any contracting agency until the agency elects to be subject to the provision of this section by amendment to its contract made in the manner prescribed for approval of contracts, except an election among the employees is not required, or, in the case of contracts made after March 1, 1982, by express provision in the contract making the contracting agency subject to the provisions of this section. The amendments to this section made during the second year of the 1999-2000 Regular Session shall apply to contracts subject to this section on January 1, 2001.