California Code, Government Code - GOV § 20303

(b)(1) For the purpose of this section only, persons who are receiving pensions, retirement allowances, or other payments, from any source whatever, because of service rendered to an employer other than the state and while they were not in state service, are not, because of that receipt, members of any other retirement or pension system.

(2) For the purposes of this section only, persons who participate in a deferred compensation plan established pursuant to Chapter 4 (commencing with Section 19993) or Chapter 8.6 (commencing with Section 19999.3) of Part 2.6 or pursuant to Article 1.1 (commencing with Section 53212) of Chapter 2 of Part 1 of Division 2 of Title 5, are not, because of that participation, members of any other retirement or pension system.

(3) For the purposes of this section only, persons who participate in a money purchase pension plan and trust that meets the requirements of Section 401(a) of Title 26 of the United States Code are not, because of that participation, members of any other retirement or pension system, so long as the contracting agency has received a ruling from the Internal Revenue Service stating that the money purchase pension plan and trust qualifies under Section 401(a) and furnishes proof thereof upon request by the board.

(4) For the purposes of this section only, persons who participate in a supplemental defined benefit plan maintained by their employer that meets the requirements of Section 401(a) of Title 26 of the United States Code are not, because of that participation, members of another retirement or pension system, provided that all of the following conditions exist:

(5) For purposes of this section only, a person who elects membership pursuant to Section 20326 is deemed, with respect to service with the California National Guard, not to be a member of any other retirement or pension system.