Cal. Gov. Code § 31836
"Service," solely for purposes of qualification for payment of benefits and retirement allowances, shall also include service as an employee of the state or a contracting agency under the Public Employees' Retirement System or of another county having a retirement system established under this chapter, or as a member of the State Teachers' Retirement System, or as a member of a retirement system of any other public agency of the state that has established reciprocity with the Public Employees' Retirement System subject to the conditions of Section 31840.2, if the compensation for such service constitutes compensation earnable or pensionable compensation pursuant to Section 7522.34, whichever is applicable, by a member under Section 31835 of this part.
No credit shall be granted in this retirement system for service for which the member has received credit in another retirement system or for which he or she is presently receiving a retirement allowance from another retirement system.
Ca. Gov. Code § 31836