California Code, Labor Code - LAB § 3717.1

In any claim in which an alleged uninsured employer is a corporation, the director may cause substantial shareholders and parents, as defined by Section 3717, to be joined as parties.  Substantial shareholders may be served as provided in this division for service on adverse parties, or if they cannot be found with reasonable diligence, by serving the corporation.  The corporation, upon this service, shall notify the shareholder of the service, and mail the served document to him or her at the shareholder's last address known to the corporation.