California Code, Government Code - GOV § 31840.5

The provisions of this chapter extending rights to a member of a county retirement system established under this chapter or subjecting him to any limitation, by reason of his membership in the Public Employees' Retirement System shall also apply to members who terminated state employment and became employees of a district within six months of such termination and who were employees of such district at the time that the district became subject to the county retirement system.  Any change in a member's contribution rate shall become effective on January 1, 1977, and a member whose rate is reduced shall not be entitled to any payment with respect to his rate of contribution prior to that date.

This section shall not be operative in any county until such time as the board of supervisors shall, by resolution adopted by majority vote, make the provisions of this section applicable in such county.