Cal. Food & Agric. Code § 21743
Any person that is engaged in the business of selling cattle on consignment at any public stockyard, public salesyard, or public cattle sales market shall prepare a certificate of consignment on or before the day of a sale which contains all of the following:
(d) Signature of the owner or his agent.
The certificate of consignment shall be kept by the seller for a period of one year after the date of sale. Any such certificate shall be exhibited on the demand of any peace officer or any agent of the department.