Cal. Ins. Code § 10210

The policy shall contain a provision that to the groups or classes originally insured there will be added from time to time all new employees of the employer eligible for insurance in such groups or classes, except that the policy may provide that if the premium is paid by the employer and employees jointly any employee who fails to request insurance during the period of eligibility following his employment as prescribed by the policy shall not be insured until he has furnished evidence of insurability satisfactory to the insurer.