California Code, Vehicle Code - VEH § 16053

(a) The department may in its discretion, upon application, issue a certificate of self-insurance when it is satisfied that the applicant in whose name more than 25 motor vehicles are registered is possessed and will continue to be possessed of ability to pay judgments obtained against him or her in amounts at least equal to the amounts provided in Section 16056.  The certificate may be issued authorizing the applicant to act as a self-insurer for either property damage or bodily injury or both.  Any person duly qualified under the laws or ordinances of any city or county to act as self-insurer and then acting as such, may upon filing with the department satisfactory evidence thereof, along with the application as may be required by the department, be entitled to receive a certificate of self-insurance.

(b) Upon not less than five days' notice and a hearing pursuant to the notice, the department may upon reasonable grounds cancel a certificate of self-insurance.  Failure to pay any judgment within 30 days after the judgment has become final and has not been stayed or satisfied shall constitute a reasonable ground for the cancellation of a certificate of self-insurance.