Unless otherwise provided by law, the board of supervisors may provide for the payment of reasonable and necessary expenses of, and of special allowances such as per meeting stipends to, members of commissions, boards, or committees appointed by it, except that no such additional expenses or special allowances shall be paid to such a member who is also a member of the board of supervisors.
Source:
Section 31000.2, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV§ionNum=31000.2..