Ghost Gun and Precursor Part Definitions

California has enacted a series of laws creating one of the most comprehensive regulatory frameworks for unserialized firearms and precursor parts in the nation. The definitional provisions are spread across multiple Penal Code sections and have been amended by several legislative acts.^[1]

Firearm Precursor Part (PC 16531)

Section 16531 defines "firearm precursor part" as a component of a firearm that is necessary to build or complete a firearm. Effective July 1, 2022, this definition was expanded by AB 1057 to include unfinished frames and receivers. The DOJ maintains a list of items classified as firearm precursor parts, which currently includes unfinished frames, unfinished receivers, unfinished handgun frames, and unfinished long gun receivers at any stage of manufacture. Precursor parts are subject to the same vendor licensing requirements, DROS fee, and background check requirements as finished firearms.^[2]

Self-Manufactured Firearms and Serialization (AB 857)

AB 857 (2016) requires any person who manufactures or assembles a firearm to first apply to the DOJ for a unique serial number or other mark of identification and to engrave or permanently affix that number to the firearm before completing the manufacturing process. This requirement applies regardless of whether the person intends to sell the firearm. The law effectively eliminated the ability to legally possess a home-built firearm without a serial number in California.^[3]

Precursor Part Vendor Requirements (AB 1057)

AB 1057 (2020, effective July 1, 2022) expanded the regulatory framework to cover firearm precursor parts. Under this law, precursor parts may only be sold through licensed firearms dealers or licensed ammunition vendors. All sales require a background check processed through the DOJ. Online purchases of precursor parts must be shipped to a licensed dealer for transfer. The law brought precursor parts into the same point-of-sale regulatory framework that applies to complete firearms.^[4]

Expanded Definitions Under SB 53

SB 53 (2023) further refined the definitions and expanded the scope of regulation. The bill clarified the definition of what constitutes a precursor part at various stages of manufacture, addressing the question of when a raw piece of metal or polymer becomes a regulated item. It also enhanced penalties for violations and strengthened reporting requirements for lost or stolen precursor parts.^[5]