California Code, Penal Code - PEN § 29300

(a) Except as provided in subdivision (c), a firearm of any nature owned or possessed in violation of Chapter 1 (commencing with Section 29610), Chapter 2 (commencing with Section 29800), or Chapter 3 (commencing with Section 29900) of Division 9 of this title, or Chapter 3 (commencing with Section 8100) of Division 5 of the Welfare and Institutions Code, or used in the commission of any misdemeanor as provided in this code, any felony, or an attempt to commit any misdemeanor as provided in this code or any felony, is, upon a conviction of the defendant or upon a juvenile court finding that an offense which would be a misdemeanor or felony if committed by an adult was committed or attempted by the juvenile with the use of a firearm, a nuisance, and is subject to Sections 18000 and 18005.

(b) A finding that the defendant was guilty of the offense but was insane at the time the offense was committed is a conviction for the purposes of this section.

(c) A firearm is not a nuisance pursuant to this section if the firearm owner disposes of the firearm pursuant to Section 29810.

(d) This section does not apply to any of the following: