Cal. Penal Code § 16519

“Federally regulated firearm precursor part” means any firearm precursor part deemed to be a firearm pursuant to Chapter 44 (commencing with Section 921) of Title 18 of the United States Code and regulations issued pursuant thereto, and, if required, has been imprinted with a serial number by a federal licensee authorized to serialize firearms in compliance with all applicable federal laws and regulations.