California Code, Government Code - GOV § 19173

(a) Any probationer may be rejected by the appointing power during the probationary period for reasons relating to the probationer's qualifications, the good of the service, or failure to demonstrate merit, efficiency, fitness, and moral responsibility, but he or she shall not be rejected for any cause constituting prohibited discrimination as set forth in Sections 19700 to 19703, inclusive.

(b) A rejection during probationary period is effected by the service upon the probationer of a written notice of rejection which shall include:  (A) an effective date for the rejection that shall not be later than the last day of the probationary period;  and (B) a statement of the reasons for the rejection.  Service of the notice shall be made prior to the effective date of the rejection, as defined by board rule for service of notices of adverse actions.  Notice of rejection shall be served prior to the conclusion of the prescribed probationary period.  The probationary period may be extended when necessary to provide the full notice period required by board rule.  Within 15 days after the effective date of the rejection, a copy thereof shall be filed with the board.