California Code, Public Utilities Code - PUC § 8107

In any civil or criminal action or proceeding for violation of the Cartwright Act (Chapter 530, Statues  1 of 1907), Part 2 of Division 7 of the Business and Professions Code,  2 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 this article or an order issued under it and in furtherance of the purposes and provisions of this article is a complete defense in such action or proceeding.