California Code, Labor Code - LAB § 3750

(a) The organization of any mutual or other insurer.

(b) Any existing contract for insurance.

(c) The right of the employer to insure in mutual or other insurers, in whole or in part, against liability for the compensation provided by this division.

(d) The right to provide by mutual or other insurance, or by arrangement with his employees, or otherwise, for the payment to such employees, their families, dependents or representatives, of sick, accident, or death benefits, in addition to the compensation provided for by this division.

(e) The right of the employer to waive the waiting period provided for herein by insurance coverage.