California Code, Insurance Code - INS § 10124

(a) A self-insured employee welfare benefit plan delivered or issued for delivery in this state more than 120 days after the effective date of this section, which provides that coverage of a dependent child of an employee shall terminate upon attainment of the limiting age for dependent children specified in the policy or contract, shall also provide in substance that attainment of the limiting age shall not operate to terminate the coverage of the child while the child is and continues to be both (1) incapable of self-sustaining employment by reason of an intellectual disability or physical handicap and (2) chiefly dependent upon the employee for support and maintenance, provided proof of the incapacity and dependency is furnished to the employer or employee organization providing the plan or program of benefits by the employee within 31 days of the child's attainment of the limiting age and subsequently as may be required by the employer or employee organization, but not more frequently than annually after the two-year period following the child's attainment of the limiting age.

(b) As used in this section, “self-insured employee welfare benefit plan” means a plan or program of benefits provided by an employer or an employee organization, or both, for the purpose of providing hospital, medical, surgical, nursing, or dental services, or indemnification for the costs incurred for these services, to the employer's employees or their dependents.