California Code, Penal Code - PEN § 18205

(a) Every person who owns or possesses a firearm or ammunition with knowledge that they are prohibited from doing so by a temporary emergency gun violence restraining order issued pursuant to Chapter 2 (commencing with Section 18125), an ex parte gun violence restraining order issued pursuant to Chapter 3 (commencing with Section 18150), a gun violence restraining order issued after notice and a hearing issued pursuant to Chapter 4 (commencing with Section 18170), or by a valid order issued by an out-of-state jurisdiction that is similar or equivalent to a gun violence restraining order described in this division, is guilty of a misdemeanor and shall be prohibited from having custody or control of, owning, purchasing, possessing, or receiving, or attempting to purchase or receive, a firearm or ammunition for a five-year period, to commence upon the expiration of the existing gun violence restraining order.

(b) For purposes of this section, a valid order issued by an out-of-state jurisdiction that is similar or equivalent to a gun violence restraining order described in this section must be issued upon a showing by clear and convincing evidence that the person poses a significant danger of causing personal injury to themselves or another because of owning or possessing a firearm or ammunition.