California Code, Government Code - GOV § 31680.16

(a) Notwithstanding Section 31680, this section shall apply to a retired person who is receiving a retirement benefit from a county retirement system and is appointed or elected to either of the following:

(b) A person who is retired under this chapter may serve as a nonsalaried member of a board or commission without reinstatement from retirement or loss or interruption of benefits under this chapter or the California Public Employees' Pension Reform Act of 2013 (Article 4 (commencing with Section 7522) of Chapter 21 of Division 7 of Title 1), provided the appointment or election is to a part-time board or commission. A retired person whose service without reinstatement is authorized by this subdivision shall not acquire benefits, service credit, or retirement rights with respect to the appointment or election, but may receive any per diem that is authorized to all members of the board or commission.