California Code, Insurance Code - INS § 10235.51

(a) Every policy or certificate shall include a provision that gives the insured the option to elect, no less frequently than on each anniversary date after the policy or certificate is issued, to pay an extra premium for one or more riders that increase coverage in any of the following ways:

(b) The premiums for the riders to increase coverage may be based on the attained age of the insured. The premium for the original policy or certificate will not be changed and will continue to be based on the insured's age when the original policy or certificate was issued.

(c) The insurer may require the insured to undergo new underwriting, in addition to the payment of an additional premium, to qualify for the additional coverage. The insurer may restrict the age for issuance of additional coverage and restrict the aggregate amount of additional coverage an insured may acquire to the maximum age and coverage the insurer allows when issuing a new policy or certificate.