Cal. Penal Code § 23900

Any person who changes, alters, removes, or obliterates the name of the maker, model, manufacturer’s number, or other mark of identification, including any distinguishing number or mark assigned by the Department of Justice, on any pistol, revolver, or any other firearm, without first having secured written permission from the department to make that change, alteration, or removal shall be punished by imprisonment pursuant to subdivision (h) of Section 1170.