Cal. Penal Code § 2881

No person, firm, partnership, association or corporation within this State shall sell or offer, trade, consign, keep, expose or display for sale any goods, wares or merchandise manufactured, assembled, produced or mined in whole or in part by prisoners in any penitentiary, prison, reformatory or other establishment in which prison labor is employed, unless such prison-made goods, wares, or merchandise are plainly, legibly, conspicuously and indelibly branded, molded, embossed, stenciled or labeled with the words “Convict-made” in plain, bold letters followed by the name of such penitentiary, prison, reformatory or other establishment in which the goods, wares or merchandise were made.