Pen. Code, § 25600

(a) A violation of Section 25400 is justifiable when a person who possesses a firearm reasonably believes that person is in grave danger because of circumstances forming the basis of a current restraining order issued by a court against another person who has been found to pose a threat to the life or safety of the person who possesses the firearm. This section may not apply when the circumstances involve a mutual restraining order issued pursuant to Division 10 (commencing with Section 6200) of the Family Code absent a factual finding of a specific threat to the person’s life or safety. It is not the intent of the Legislature to limit, restrict, or narrow the application of current statutory or judicial authority to apply this or other justifications to a defendant charged with violating Section 25400 or committing another similar offense.

(b) Upon trial for violating Section 25400, the trier of fact shall determine whether the defendant was acting out of a reasonable belief that the defendant was in grave danger.