Cal. Lab. Code § 1188

Any person aggrieved directly or indirectly by any final rule or regulation of the commission made under this chapter may apply to the commission for a rehearing in respect to any matters determined or covered therein and specified in the application for rehearing within twenty days after the publication thereof. The application for rehearing shall be verified and shall state fully the grounds upon which the application for rehearing is based. The commission upon considering an application for rehearing may grant the same by order and notice thereof given by mail to the party applying for the rehearing, and fix a time for the rehearing and reconsider its order, rule, or regulation. The commission may redetermine the matter upon the record before it and give notice of its redetermination in the same manner as provided for service of an original order, rule, or regulation. The commission may deny such rehearing upon the record before it, giving notice of its decision by mail to the applicant therefor. Such rehearing is deemed to be denied unless acted upon by the commission within thirty days after being filed.