Cal. Penal Code § 23920

Except as provided in Section 23925, any person who, with knowledge of any change, alteration, removal, or obliteration described in this section, buys, receives, disposes of, sells, offers for sale, or has in possession any pistol, revolver, or other firearm that has had the name of the maker or model, or the manufacturer’s number or other mark of identification, including any distinguishing number or mark assigned by the Department of Justice, changed, altered, removed, or obliterated, is guilty of a misdemeanor.