California Penal Code 23920 makes it a misdemeanor to possess, buy, receive, sell, offer for sale, or transfer a firearm whose identification marks have been altered, and, since January 1, 2024, to knowingly possess any firearm that never had a valid serial number at all. Both violations carry up to six months in county jail, a fine of up to $1,000, or both.1California Legislative Information. California Penal Code 19 The knowledge requirements and available exceptions differ between the two halves of the statute, and the same conduct can also trigger a federal felony.
The Two Prohibitions in Section 23920
Subsection (a) targets tampering. It applies to anyone who buys, receives, sells, offers for sale, or possesses a firearm whose identification marks have been altered. The firearm doesn’t need to change hands permanently. Simply offering it for sale is enough. Possession here covers both carrying the firearm on your person and having it somewhere you control, like a nightstand, vehicle console, or storage unit.
Subsection (b) is newer and covers a different problem. Effective January 1, 2024, knowingly possessing any firearm that lacks a valid state or federal serial number is independently a misdemeanor. This provision reaches unserialized homemade firearms and ghost guns that were never marked in the first place, rather than factory firearms whose markings were later defaced.
Which Markings the Statute Protects
The law protects the markings that trace a firearm to its origin: the manufacturer’s name, the model designation, the manufacturer’s serial number on the frame or receiver, and any distinguishing number assigned by the California Department of Justice. The DOJ-assigned numbers matter because California requires owners of homemade firearms to apply for a unique serial number, and those assigned numbers carry the same legal protection as factory markings.
Any tampering that renders these marks illegible qualifies. Grinding down a serial number, scratching digits to change them, or removing the portion of metal that contains the markings all count. Even partial obscuring of a single character can cross the line.
What Prosecutors Have to Prove About Your Knowledge
Both subsections require knowledge. Under subsection (a), the prosecution must prove you were aware the identification marks had been tampered with when you possessed, bought, or sold the weapon. Under subsection (b), the prosecution must show you knowingly possessed a firearm you knew lacked a valid serial number.
This is the most common line of defense. If you inherited a firearm, bought one at a swap meet, or found one in a storage unit without realizing the serial number was ground off, the case gets harder for the state. Courts look at the totality of circumstances. If the tampering is obvious to anyone who handles the firearm, claiming ignorance becomes a hard sell. Statements you made, how you acquired the weapon, what you paid for it, and whether the defacement was visible to the naked eye all factor in.
Penalties and Firearm Rights After a Conviction
A violation of either subsection is a straight misdemeanor. Because the statute does not prescribe its own punishment, the default under Penal Code 19 applies: up to six months in county jail, a fine of up to $1,000, or both.1California Legislative Information. California Penal Code 19 Judges can also grant misdemeanor probation, which may substitute community service or specific conduct restrictions for jail.
The record can matter more than the sentence. California imposes a 10-year firearm prohibition on people convicted of certain firearm-related misdemeanors.2California Department of Justice. Firearms Prohibited Categories Whether a conviction under Penal Code 23920 specifically triggers that prohibition depends on whether the offense appears in the enumerated list under Penal Code 29805. If it applies, you lose the legal ability to buy or possess any firearm in California for a decade after conviction.
Who Is Exempt and How to Surrender a Firearm Safely
Penal Code 23925 carves out exceptions that apply to both subsections. Military personnel and peace officers are exempt while on duty and acting within the scope of their employment. Forensic lab employees handling evidence firearms are exempt while on duty. And a person not otherwise prohibited from possessing firearms may possess one with altered markings long enough to deliver it to a law enforcement agency, provided the firearm is transported in a locked container and the agency is notified beforehand.3California Legislative Information. California Penal Code 23925 – Firearms
Subsection (b), the unserialized firearm provision, has additional exceptions. Non-handgun firearms made or assembled before December 16, 1968, are exempt, as are firearms classified as curios, relics, or antiques under federal regulations. Federally licensed manufacturers, importers, and other licensees authorized to serialize firearms are exempt. People who applied to the DOJ for a unique serial number before January 1, 2024, remain exempt as long as they comply with all requirements, including engraving the assigned number within 10 days of receiving it.4California Legislative Information. AB 1621 – California Legislative Information New residents who move to California with an unserialized firearm are exempt if they apply to the DOJ for a serial number within 60 days of arrival and then follow through on the serialization requirements.
The safe harbor for surrendering a firearm is worth using promptly. Once you realize the markings are defaced or the serial number is missing, the knowledge element for the underlying offense is satisfied, and keeping the firearm indefinitely puts you in the zone the statute punishes. The practical steps are to contact your local law enforcement agency, tell them you want to surrender the firearm, and follow their instructions for bringing it in.
Federal Exposure Under 18 U.S.C. 922(k)
The same conduct can be a federal crime, and the federal penalty is much heavier. Under 18 U.S.C. ยง 922(k), it’s illegal to possess or receive any firearm with a removed, obliterated, or altered serial number if that firearm has at any point been shipped or transported across state lines.5Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts Since virtually every commercially manufactured firearm crosses state lines between factory and retail, that requirement is almost always met.
A federal conviction carries up to five years in prison.6Office of the Law Revision Counsel. 18 USC 924 – Penalties A single defaced firearm in California can produce both a state misdemeanor charge and a federal felony prosecution. Federal prosecutors more often pick these cases up when other charges are involved, like drug trafficking or felon-in-possession counts, but they have the authority to bring the serial number offense on its own.