California Code, Penal Code - PEN § 2886

Any person, firm, partnership, association or corporation within this State, when advertising in any periodical or publication any goods, wares or merchandise made in whole or in part by prisoners in any penitentiary, prison, reformatory or other establishment in which prison labor is employed, must insert the words “Convict-made,” in such advertisement in type or other letters conforming in size or shape to those used in the text of said periodical or publication.