Cal. Gov. Code § 31483

Notwithstanding any other provision of law, whenever the governing body of a county or district has made a particular provision or provisions of this chapter applicable in such county or district through the adoption of an ordinance or resolution, such governing body may at any time thereafter adopt a further ordinance or resolution terminating the applicability of such provision or provisions as to employees of the county or district whose services commence after a given future date specified in the latter ordinance or resolution.