California Code, Business and Professions Code - BPC § 16801

It is unlawful for any corporation organized under the laws of this State, or the board of directors, trustees, stockholders, agents, or officers of any corporation, to pass or enforce any rule, by-law, or regulation whereby any officer, stockholder, member, shareholder, agent, servant thereof, or any other person in any way interested in or connected with such corporation shall in any respect be prohibited, prevented, or enjoined from buying livestock in any market in this State where livestock is brought to be sold.

Every such rule, regulation, or by-law is declared to be contrary to the public policy of this State, and is unlawful and void. Any person who attempts, directly or indirectly, to enforce any such rule, regulation, or by-law, is guilty of a misdemeanor and subject to the penalties prescribed in this chapter.