Cal. Food & Agric. Code § 65671

In any civil or criminal action or proceeding for violation of the Cartwright Act (Section 16700, Business and Professions Code, and following), the Unfair Practices Act (Section 17000, Business and Professions Code, and following), the Fair Trade Act (Section 16900, Business and Professions Code, and following), Section 1673 of the Civil Code, or any rule of statutory or common law against monopolies or combinations in restraint of trade, proof that the act complained of was done in compliance with the provisions of this chapter or a rule or regulation of the commission issued under this chapter and in furtherance of purposes and provisions of this chapter, shall be a complete defense to such action or proceeding.