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Laws Governing Self-Assemblyof Firearms

In 2016, California enacted a law placing new requirements on anyone who manufactures or assembles a firearm or otherwise possesses an unserialized firearm but does not have a valid firearm manufacturer’s license. This law became effective in 2018, and requires that:

  • Prior to assembling or manufacturing a firearm, a person must apply to the California Department of Justice (“DOJ”) for a unique serial number or mark of identification unique to that firearm.1 State law directs DOJ to issue serial numbers to applicants who meet all of the following requirements: (1) have a firearm safety certificate, (2) have completed a firearms eligibility background check verifying that they are eligible to possess firearms under both state and federal law, (3) presented 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.2
  • After receiving that serial number from DOJ, the person must engrave or permanently affix the unique serial number to their firearm within 10 days of manufacturing or assembling the firearm.3
  • The individual must provide information about the newly serialized firearm, including the identity of the owner of the firearm, to DOJ.4 Firearms manufactured or assembled pursuant to these provisions are for personal use only and generally cannot be sold or transferred.5
  • Anyone in possession of an unserialized firearm must apply to the DOJ for a serial number and must serialize the firearm, or must otherwise relinquish the unserialized firearm to law enforcement.6
  • The law also expressly prohibits individuals or companies from knowingly allowing, facilitating, aiding, or abetting the manufacture or assembly of a firearm by individuals prohibited from possessing a firearm under state law.7
  • In addition, self-assembled firearms must be compliant with the requirements of California’s Unsafe Handgun Act, which requires that handguns incorporate certain consumer and public safety features. See our Design Safety Standards in California policy summary for a comprehensive discussion of these requirements under the Unsafe Handguns Act.

Laws Governing the Sale of Ghost Gun Components

The California laws described above govern the assembly and manufacture of ghost guns by people who are not otherwise licensed to manufacture firearms, but California currently includes few protections governing the sale of ghost gun components. As a result, individuals who would not otherwise be able to pass a background to legally purchase firearms or ammunition weapons have increasingly exploited California’s failure to regulate the sale of unfinished firearm frames and receivers commonly used to assemble ghost guns, contributing to a dangerous exploding market for these products within the state.

In 2019, California finally acted to address this threat to public safety by enacting legislation that will, when implemented upon its effective date, begin to meaningfully regulate the sale of unfinished firearm frames and receivers. 8 (This legislation was originally set to go into full effect in July 2025, but California passed a law in 2020 to expedite implementation of most of these new ghost gun requirements to July 1, 2022).9

Once in effect, this law will treat the sale of unfinished frames and receivers (defined as “firearm precursor parts”) in a manner similar to the sale of ammunition under California law by requiring:

  • Sellers of firearm precursor parts to obtain a state business license (called a “firearm precursor part vendor license”) to sell more than one precursor part in any 30-day period;10
  • Sales of precursor parts by any party to be conducted in-person through licensed precursor part vendors, pursuant to a background check and sale record;11
  • Licensed precursor part vendors to comply with other public safety laws similar to those governing firearm dealers and ammunition vendors under California law, including ensuring employees who handle firearm precursor parts regularly pass background checks and restrictions on trafficking of firearm precursor parts or delivery of such products to minors under 21 and other people ineligible to receive them.12

 For more information about undetectable and untraceable firearms, see our Ghost Guns policy page. 

  1. Cal. Penal Code §§ 29180(b)(1); 29182.[]
  2. Cal. Penal Code §§ 29182(b).[]
  3. Cal. Penal Code §§ 29180(b)(1); 29180(b)(2)(A). 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. Cal. Penal Code § 29180(b)(2)(B).[]
  4. Cal. Penal Code. § 29180(b)(3).[]
  5. Cal. Penal Code § 29180(d).[]
  6. Cal. Penal Code § 29180(c).[]
  7. Cal. Penal Code § 29180(f).[]
  8. See 2019 CA AB 879.[]
  9. 2019 CA SB 118, Sec. 21 – 37.[]
  10. Cal. Penal Code §§ 30442; 30485; 16532[]
  11. Cal. Penal Code §§ 30412; 30414; 30452[]
  12. See Cal. Penal Code §§ 30400 – 30495.[]