Cal. Business and Professions Code § 22949.66

(a) A defendant against whom an action is brought under Section 22949.65 does not have standing to assert the right of another individual to keep and bear arms under the Second Amendment to the United States Constitution as a defense to liability under that section unless either of the following is true: (1) The United States Supreme Court holds that the courts of this state must confer standing on that defendant to assert the third-party rights of other individuals in state court as a matter of federal constitutional law. (2) The defendant has standing to assert the rights of other individuals under the tests for third-party standing established by the United States Supreme Court. (b) A defendant in an action brought under Section 22949.65 may assert an affirmative defense to liability under this section if both of the following are true: (1) The defendant has standing to assert the third-party right of an individual to keep and bear arms in accordance with subdivision (a). (2) The defendant demonstrates that the relief sought by the claimant will violate a third-party’s rights under the Second Amendment to the United States Constitution right as defined by clearly established case law of the United States Supreme Court. (c) Nothing in this section shall in any way limit or preclude a defendant from asserting the defendant’s personal constitutional rights as a defense to liability under Section 22949.65, and a court shall not award relief under Section 22949.65 if the conduct for which the defendant has been sued was an exercise of a state or federal constitutional right that personally belongs to the defendant.