Cal. Pub. Util. Code § 5379.5

The commission may, on a complaint alleging that any corporation or person is operating as a charter-party carrier of passengers without a valid certificate or permit in violation of this chapter, or on its own motion without a complaint, with or without notice of a hearing, order the corporation or person so operating to cease and desist from that operation until the commission makes and files its decision in the matter or until further order of the commission.