California Code, Public Utilities Code - PUC § 2891.2

Telephone subscribers shall be annually notified that use of an “800” or “900” telephone number may result in the disclosure of the subscriber's telephone number to the called party. The commission shall, by rule or order, impose the responsibility for the notification with the telephone corporation that offers the caller identification service, often known as automatic number identification, in connection with an “800” or “900” service.