Cal. Penal Code § 17505

It shall be unlawful for any person, as defined in Section 16970, to advertise the sale of any weapon or device, the possession of which is prohibited by Section 18710, 20110, 30315, 30320, 32625, or 33410, by Article 2 (commencing with Section 30600) of Chapter 2 of Division 10 of Title 4, or by any provision listed in Section 16590, in any newspaper, magazine, circular, form letter, or open publication that is published, distributed, or circulated in this state, or on any billboard, card, label, or other advertising medium, or by means of any other advertising device.