California Code, Penal Code - PEN § 2884

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 those prison-made goods, wares, or merchandise have first been disinfected or sterilized in a plant located in California and licensed by the State Department of Health Services in accordance with any regulations of the State Department of Health Services now in force or which later may be made effective.

It is hereby further provided that certificate of that disinfection or sterilization must accompany, be stamped on or attached to those goods, wares, or merchandise in a manner or form prescribed by the officials of the State of California responsible for the enforcement of this article.