California Code, Government Code - GOV § 26946

The provisions of this article shall become effective in only those counties in which, prior to the first day of the period for filing declarations of candidacy for the office of county auditor, the board of supervisors by a unanimous vote, at a regular meeting with all members present, enacts an ordinance adopting the provisions of this article.  The ordinance so adopted may be repealed by the board of supervisors at any time.