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California has been the epicenter of a devastating and fast-growing ghost gun crisis as ghost gun companies sought to exploit legal loopholes in the definition of the word “firearm” itself to sell unfinished DIY gun build kits and other products designed to circumvent California’s strong gun safety laws. In 2022, California built on some narrower laws by enacting comprehensive legislation to strongly reform and regulate the ghost gun industry and address this crisis.1 Many of California’s new ghost gun reforms took effect immediately when the Governor signed AB 1621 into law on June 30, 2022, while some other critical provisions will become effective on January 1, 2023. Critically, these laws will ensure that the sale and manufacture of both completed and unfinished frames and receivers (called “firearm precursor parts” in California law) are subject to the same critical gun safety laws as fully assembled guns, and that many more unlicensed gun manufacturers must obtain standard manufacturer licenses and comply with stronger safety requirements in order to lawfully produce firearms in the state.

Laws Governing the sale of ghost gun kits and components

In 2022, California enacted much stronger laws to regulate the sale of ghost gun kits and key components, including many reforms that took effect immediately on June 30, 2022.2

As a result, California law now generally treats the sale, transfer, and manufacture of both completed and unfinished frames or receivers (defined as “firearm precursor parts”) the same way state law treats the sale, transfer, and manufacture of fully assembled guns.3 Among other things, this means that the sale and transfer of ownership of unfinished frames or receivers in California must now generally be conducted by or through a licensed firearms dealer, pursuant to requirements such as an in-person ID check, background check, sale record, firearm safety certificate check, bulk purchase limitations, and waiting periods. This also means that all people who are legally disqualified from purchasing or obtaining fully assembled firearms (due to age, criminal history, court order, etc.) are legally disqualified from purchasing or obtaining both completed and unfinished frames or receivers as well.

Importantly, California law now defines unfinished frames or receivers more broadly too, to include “any forging, casting, printing, extrusion, machined body or similar article that has reached a stage in manufacture where it may readily be completed, assembled or converted to be used as the frame or receiver of a functional firearm, or that is marketed or sold to the public to become or be used as the frame or receiver of a functional firearm once completed, assembled or converted.”4

California law also now makes it generally unlawful to:

  • Sell or transfer ownership of an unserialized firearm (including a completed or unfinished frame or receiver)5 that does not have a federal serial number imprinted by a federal firearms manufacturer or importer (or other licensee authorized to serialize firearms under federal law).6

    (California enacted mirroring prohibitions in the Business and Professions Code, making it generally unlawful (starting January 1, 2023) for any person within California to “manufacture or cause to be manufactured, distribute, transport, or import into the state, or cause to be distributed, transported, or imported into the state, keep for sale, offer or expose for sale, or give or lend” any firearm that does not have a serial number required by law, or which has had its serial number altered or obliterated.7
  • Sell, offer to sell, purchase, or transfer ownership of any unfinished frame or receiver that is not (a) deemed to be a “firearm” under federal law and (b) accordingly, imprinted with a federal serial number by by a federal firearms manufacturer or importer (or other licensee authorized to serialize firearms under federal law), if required under federal law.8 (This change helps to ensure that these products may be sold in California only if they have valid federal serial numbers and that the California Department of Justice may access FBI NICS background check records to conduct a full background check for individuals seeking to buy these products).

    (California enacted mirroring prohibitions in the Business and Professions Code (effective January 1, 2023) on purchasing, selling, offering to sell, or transferring ownership of any unfinished frame or receiver that is not deemed a firearm under federal law.9

LAWS requiring a license to manufacture firearms

Effective January 1, 2023, California law will require any person, firm, or corporation to obtain a firearm manufacturer’s license from the California Department of Justice, and comply with specified laws governing licensed firearm manufacturers, in order to legally manufacture more than three firearms in the state in a calendar year, or to use a 3D-printer10 to manufacture any number of firearms.((See Cal. Pen Code § 29010 (as amended by 2022 CA AB 2156). For the purposes of this and other relevant gun safety laws, the term “firearm” is defined to include both a completed or unfinished frame or receiver (defined as a “firearm precursor part”).11People without a firearm manufacturers license may produce up to three firearms in a calendar year solely for personal use, provided they do not use a 3D printer or (as discussed below) a CNC milling machine to do so, and provided they comply with other requirements detailed below.

To qualify for a California firearm manufacturer’s license, applicants must possess a federal firearm manufacturer’s license from ATF as well.12 Previously (and until January 1, 2023), California law required people to obtain a state firearm manufacturer’s license from the Department of Justice and comply with manufacturer requirements only if they had a federal firearm manufacturer’s license and manufactured at least 50 firearms in a calendar year in the state.

California-licensed manufacturers are required, among other things, to:

  • Conduct manufacturing operations only in designated buildings that meet site security standards to prevent gun thefts, or to deter false claims that trafficked guns were stolen from those premises;
  • Ensure that all firearms, frames or receivers, and unfinished frames or receivers produced by the manufacturer are stamped with a unique serial number to aid in investigation of gun crimes and trafficking;
  • Ensure that all employees who handle firearms pass annual background checks;
  • Notify local law enforcement that the manufacturer will be manufacturing firearms in a designated location and allow routine inspections to ensure the licensee operates legally; and
  • Retain manufacturing records identifying all firearms, frames, and unfinished frames they produce.13

CNC milling machines: As noted above, California law will require a state and federal firearm manufacturer’s license to lawfully use a 3D printer to manufacture a firearm, effective January 1, 2023. Effective June 30, 2022, California law also similarly requires any person, firm, or corporation to have at a minimum, a valid federal firearms manufacturer or importer license in order to use a computer numerical control (CNC) milling machine to manufacture a firearm, including a completed or unfinished frame or receiver.14 These CNC milling machines allow people to carve firearms or firearm components from chunks of metal or other material with the press of a button and have been specifically designed to circumvent laws regulating the sale of firearms and unfinished frames and receivers.

California law now also makes it generally unlawful to sell, offer to sell, or transfer a CNC milling machine or 3D printer that has the sole or primary function of manufacturing firearms to any person who does not have a federal firearms manufacturer or importer license, and makes it unlawful for people without such a license to possess, purchase, or receive a CNC milling machine that has the sole or primary function of manufacturing firearms.15

Laws Governing unlicensed Firearm manufacturers

As noted above, California law now generally requires that any frame or receiver (including any unfinished product that is marketed or sold to the public to become or be used as the frame or receiver of a functional firearm once completed, assembled or converted)16 must be imprinted by a federal firearms license holder with a valid federal serial number prior to sale to the general public.17 As a result, it is expected that most people lawfully assembling firearms will do so from products that were already imprinted with serial numbers prior to sale.

However, any person manufacturing or assembling a firearm from unserialized products they already obtained or from other sources where the frame or receiver of the firearm is not validly serialized must apply to the California Department of Justice for a unique serial number prior to manufacturing or assembling the firearm or completing the frame or receiver.18 In these circumstances, the person must provide specified information about the firearm the applicant intends to produce, pass a background check and other qualification standards to receive a serial number from the Department,19 engrave or permanently affix that serial number onto the firearm within 10 days of manufacturing or assembling the firearm, and verify that they complied by notifying the Department of Justice in a manner and time period specified by the Department.20 If the firearm is made from plastic, the serial number must be engraved or affixed on a piece of metal large enough to be detected by metal detectors and embedded within the plastic.21 People who are currently in possession of any unserialized firearm must apply for a unique serial number from the Department of Justice pursuant to these processes prior to January 1, 2024, or otherwise have their firearm serialized by a federal firearms licensee.22 Subject to narrow exceptions, itwill generally be unlawful to knowingly possess an unserialized firearm, including a completed or unfinished frame or receiver, starting on January 1, 2024. (California law already generally prohibits selling or transferring ownership of firearms, including completed and unfinished frames and receivers, that do not have federal serial numbers).23

California law now provides even clearer limitations to ensure that people manufacturing or assembling guns without a manufacturer’s license do so for personal use only. Subject to narrow exceptions, it is unlawful for any person, corporation, or firm that is not a federally licensed firearms manufacturer to sell or transfer ownership of any fully assembled gun or completed frame or receiver, if that person, corporation, or firm:

  • Manufactured or assembled the firearm;
  • Knowingly caused the firearm to be manufactured or assembled by a person, corporation, or firm that is not a federally licensed firearms manufacturer; or
  • Is aware that the firearm was manufactured or assembled by a person, corporation, or firm that is not a federally licensed firearms manufacturer.24


California’s law also makes it unlawful for any person, firm, or corporation to knowingly allow, facilitate, aid, or abet the manufacture or assembling of a firearm (including a completed frame or receiver) by a person who is legally disqualified from accessing firearms; or to knowingly manufacture or assemble, or knowingly cause, allow, facilitate, aid, or abet the manufacture or assembling of, a firearm that is not imprinted with a valid state or federal serial number.25

A separate but related law, effective January 1, 2023, makes it generally unlawful for any person within California to “manufacture or cause to be manufactured, distribute, transport, or import into the state, or cause to be distributed, transported, or imported into the state, keep for sale, offer or expose for sale, or give or lend” any firearm that does not have a serial number required by law, or which has had its serial number altered or obliterated.26 Any person other than an officer or employee of a state or local governmental entity in the state is authorized to bring a civil action against any person who knowingly violates this prohibition; who knowingly engages in conduct that aids or abets a violation, regardless of whether the person knew or should have known that the person aided or abetted would be violating the law; or who knowingly commits an act with the intent to engage in the conduct described above.27

In addition, California law does not authorize people to assemble prohibited weapons such as assault weapons, machine guns, or handguns that have not passed testing and certification requirements under California’s Unsafe Handgun Act consumer safety law.28Note: it appears that no retail sellers of ghost gun kits have complied with California’s Unsafe Handgun Act by submitting their handgun designs for testing and certification by California’s Department of Justice. The Unsafe Handgun Act requires that new handgun models incorporate specified consumer and public safety features and be tested by independent laboratories to ensure they can pass basic safety and reliability standards. It is a crime under California law to manufacture or cause the manufacture of handgun models that have not been tested and certified under this consumer protection law.29 See our Design Safety Standards in California page for a comprehensive discussion of these requirements.

Finally, legislation adopted in 2022 also requires gun show vendors to certify in writing to the gun show organizer/promoter, among other things, that they will not display, possess, or offer for sale any unserialized frame or receiver (including both completed and unfinished frames or receivers).30

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  1. See 2022 CA AB 1621, 2022 CA AB 2156, 2022 CA SB 1327, 2022 CA AB 1594, and 2022 CA AB 2552.[↩]
  2. Previously, the state had enacted some narrower laws to regulate the ghost gun industry with delayed implementation dates; most of these laws’ major provisions were slated to go into effect on July 1, 2022 but were replaced by 2022 CA AB 1621. See 2019 CA AB 879 and 2019 CA SB 118, Sec. 21 – 37.[↩]
  3. See 2022 CA AB 1621; Cal. Penal Code § 16520; 16531.[↩]
  4. Cal. Penal Code § 16531(a)(Emphasis added). California law now also provides a process authorizing the state Department of Justice to issue a determination regarding whether an item or kit meets the legal definition of “firearm precursor part” upon receiving a written request or standard form requesting this determination. See Cal. Penal Code § 30401.[↩]
  5. See Cal. Penal Code § 16520(b)(15.[↩]
  6. Cal. Penal Code §§ 27530; 16515 (defining “Federal licensee authorized to serialize firearms”).[↩]
  7. See 2022 CA SB 1327 (enacting Cal. Bus. Prof. Code §§ 22949.62(a); 22949.61(f) (defining “unserialized firearm”).[↩]
  8. See Cal. Penal Code §§ 30400; 16519 (defining “Federally regulated firearm precursor part”); 16515 (defining “Federal licensee authorized to serialize firearms”).[↩]
  9. See 2022 CA SB 1327 (enacting Cal. Bus. Prof. Code § 22949.62(b).[↩]
  10. For these purposes, a 3D-printer is defined in the law as “a computer-aided manufacturing device capable of producing a three-dimensional object from a three-dimensional digital model through an additive manufacturing process that involves the layering of two-dimensional cross sections formed of a resin or similar material that are fused together to form a three-dimensional object. Cal. Pen Code § 29010(b).[↩]
  11. See Cal. Penal Code §§ 29010(b); 16520(b)(16). “Firearm precursor part” is defined in Cal. Penal Code § 16531.[↩]
  12. Cal. Pen Code § 29050. For laws governing the process for applying for a firearm manufacturer’s license from the California Department of Justice, see California Penal Code §§ 29030 – 29075.[↩]
  13. See Cal. Penal Code §§ 29100 – 29150.[↩]
  14. Cal. Pen Code § 29185(a).[↩]
  15. Cal. Pen Code § 29185(b), (c). The new law provided a grace period for people without the required license to terminate possession of any such CNC milling machine within 90 days after June 30, 2022. Cal. Pen Code § 29185(d). The law was updated to include 3D printers in 2023; individuals without the required license must terminate possession of any such 3D printer within 90 days after July 1, 2024.[↩]
  16. See definition of “firearm” and “firearm precursor part” in Cal. Penal Code §§ 16519; 16531.[↩]
  17. Cal. Penal Code §§ 27530; 16515 (defining “Federal licensee authorized to serialize firearms”). See also, Cal. Penal Code §§ 30400 (making it generally unlawful to sell, offer to sell, purchase, or transfer ownership of any unfinished frame or receiver that is not deemed to be a “firearm” under federal law and accordingly, imprinted with a serial number by a federal firearms licensee authorized to serialize firearms if required under federal law); 16519 (defining “Federally regulated firearm precursor part”); 16515 (defining “Federal licensee authorized to serialize firearms”).[↩]
  18. See Cal. Penal Code §§ 29180(b), (c); 29182.[↩]
  19. State law now authorizes CalDOJ to issue serial numbers to applicants who meet all of the following requirements: (1) have a valid firearm safety certificate, (2) pass a firearms eligibility background check verifying that they are eligible to possess firearms under both state and federal law, (3) present proof of age and identity showing they are at least 21 years of age, and (4) provided a description of the firearm they intend to manufacture or assemble. Cal. Penal Code § 29182(b).[↩]
  20. See Cal. Penal Code §§ 29180(b), (c); 29182.[↩]
  21. Cal. Penal Code § 29180(b)(2)(B).[↩]
  22. See Cal. Pen Code §§ 29320; 23925(b)(5); 29180(c).[↩]
  23. Cal. Penal Code §§ 27530; 30400; 16515 (defining “Federal licensee authorized to serialize firearms”); 16519 (defining “Federally regulated firearm precursor part”). See also, Cal. Bus. Prof. Code §§ 22949.62(a); 22949.61(f) (defining “unserialized firearm”).[↩]
  24. Cal. Pen Code §§ 29181(d); 16520(g).[↩]
  25. Cal. Pen Code §§ 29181(e), (f); 16520(g); 17312 (defining “Valid state or federal serial number or mark of identification”.[↩]
  26. Cal. Bus. Prof. Code §§ 22949.62(a); 22949.61(f) (defining “unserialized firearm”). This prohibition also extends to the same conduct with any assault weapon or .50 MBG rifle.[↩]
  27. Cal. Bus. Prof. Code § 22949.65.[↩]
  28. Cal. Penal Code § 29182(e).[↩]
  29. Cal. Penal Code § 32000(a).[↩]
  30. Cal. Penal Code § 27305 (b), as amended by 2022 CA AB 2552, SEC. 3. (effective January 1, 2023).[↩]

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