Cal. Welf. & Inst. Code § 271

In counties having charters which provide a method of appointment and tenure of office for probation officers, assistant probation officers, deputy probation officers, and the superintendent, matron, and other employees of the juvenile hall, such charter provisions shall control as to such matters, and in counties which have established or hereafter establish merit or civil service systems governing the methods of, appointment and the tenure of office of, probation officers, assistant probation officers, deputy probation officers, and of the superintendents, matrons and other employees of the juvenile hall, the provisions of such merit or civil service systems shall control as to such matters; but in all other counties, such matters shall be controlled exclusively by the provisions of this code.