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 a firearm precursor part as a forging, casting, printing, extrusion, machined body, or similar article that may readily be completed, assembled, or converted into a functional firearm frame or receiver, or is marketed or sold to become or be used as one once completed, assembled, or converted. Parts usable only on antique firearms are excluded. AB 1621 revised this definition effective June 30, 2022, to cover qualifying unfinished articles that can become firearm frames or receivers. DOJ must provide written guidance and pictorial diagrams showing examples of firearm precursor parts. An unfinished article qualifies when it may readily be completed, assembled, or converted into a functional frame or receiver, or when it is marketed or sold for that purpose. 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) established serialization requirements for self-manufactured firearms, subject to exceptions. Under PC 29180, before manufacturing or assembling a firearm without a valid state or federal serial number or identification mark on its frame or receiver, a person must apply to DOJ for a unique serial number or other identification mark. The assigned mark must be engraved or permanently affixed within 10 days of manufacturing or assembling the firearm. This requirement applies regardless of whether the person intends to sell the firearm. AB 857 imposed serialization requirements subject to exceptions, including an exception for non-handguns made or assembled before December 16, 1968.^[3]

Precursor Part Restrictions (AB 1621)

AB 1621 revised the precursor-part framework effective June 30, 2022. California generally prohibits purchase, sale, offers to sell, or ownership transfers of precursor parts that are not federally regulated, subject to the exceptions in PC 30400 and 30420. PC 16520 includes firearm precursor parts within the definition of firearm for the dealer-transfer provisions. Where neither party has a dealer license, PC 27545 requires the transaction to be completed through a licensed firearms dealer. Upon submission of firearm purchaser information, DOJ must check whether the purchaser is prohibited from acquiring a firearm. The dealer-transfer requirement in PC 27545 applies when neither party has a dealer license, including when the purchase is arranged online. PC 16520 includes precursor parts within the firearm definition for the dealer-transfer and purchaser-check provisions.^[4]

Residential Firearm Storage Under SB 53

SB 53 (2024) established residential firearm storage requirements. Beginning January 1, 2026, a firearm possessed in a residence must be securely stored whenever it is not carried or readily controlled by the possessor or another lawful authorized user. Unloaded antique firearms and permanently inoperable firearms are exempt. A first violation carries a fine of up to $250, a second up to $500, and a third or later violation is a misdemeanor. A person is not penalized if they use a firearm safety device or gun safe they reasonably believed met the requirements. DOJ must seek to inform residents about these storage standards.^[5]