California SB 452: Microstamping Rules, Exemptions, and Challenges

California’s SB 452 microstamping law will prohibit licensed firearms dealers from selling any new semi-automatic pistol that isn’t verified as microstamping-enabled, with the restriction scheduled to take effect on January 1, 2028. That deadline is conditional: it only activates if the California Department of Justice first determines by July 1, 2027, that microstamping components or microstamping-enabled firearms are commercially available at reasonable prices.¹ Signed into law on September 26, 2023, the bill moved the microstamping requirement out of the state’s Unsafe Handgun Act and into a standalone set of rules at Penal Code sections 27531 through 27534.2.²

What Happens at the Dealer Counter in 2028

Once the restriction is live, Penal Code Section 27533 bars a licensed dealer from selling, transferring, or delivering a semi-automatic pistol unless it carries a written certification from the manufacturer or a licensed gunsmith confirming that it contains a microstamping component meeting DOJ performance standards.³ A dealer who sells a non-compliant pistol after the deadline is violating state law and risks losing their firearms dealer license.

The obligation sits at the point of sale, not on the gun itself. Under the old framework, a pistol without microstamping was defined as “unsafe” and effectively locked out of the state’s certified handgun roster. SB 452 removed that clause from Section 31910 entirely and rebuilt the requirement as a dealer restriction with a phased rollout.²

The Conditions That Must Be Met First

SB 452 built in a series of staggered milestones the DOJ has to hit before the 2028 dealer prohibition can turn on. The DOJ released its viability report on July 18, 2025, concluding that microstamping components are technologically viable and can reliably imprint unique character arrays on spent cartridge cases.² That finding kicked off the following schedule under Section 27532:

September 1, 2025: DOJ issues written performance standards for entities producing microstamping components.
January 1, 2026: DOJ begins accepting license applications from component manufacturers.
July 1, 2026: DOJ provides grants or contracts with licensed producers so components are available at reasonable cost to firearm manufacturers, dealers, and gunsmiths.
July 1, 2027: DOJ determines whether microstamping components are available at commercially reasonable prices, or whether microstamping-enabled firearms are readily available for purchase in California.

The January 1, 2028, dealer restriction only takes effect if the DOJ makes a positive availability determination by July 1, 2027.¹ If the components are not commercially available, the restriction does not activate on schedule. This is the safeguard against the sort of gridlock that froze the handgun roster under the prior law.

What’s Exempt from the Requirement

Section 27533 carves out several categories of transactions that aren’t covered by the dealer restriction, and these exemptions matter for most existing California gun owners.

Pistols manufactured or delivered to a firearms dealer before January 1, 2028, are exempt. Dealers can continue selling that pre-2028 inventory after the deadline. Private party transfers processed through a dealer under the procedures starting at Section 28050 are also exempt, so two individuals can buy and sell a handgun between themselves without the pistol needing to be microstamping-enabled, though the transfer still has to run through a licensed dealer for the background check. Transfers to gunsmiths for service, repair, or installation of a microstamping component are exempt, as are transfers to federal firearms licensees.⁴

If you already own a semi-automatic pistol without microstamping, you don’t have to retrofit it. You can also sell it to another private party through a dealer without any microstamping compliance. The law targets new commercial inventory entering the retail pipeline, not the existing stock of legally owned firearms.

Penalties for Tampering with a Microstamping Component

Penal Code Section 27534 makes it a misdemeanor to modify a microstamping-enabled pistol or its microstamping component with intent to prevent the production of a microstamp. A first offense carries up to six months in county jail, a fine of up to $1,000, or both. A second or subsequent offense carries up to one year in county jail, a fine of up to $2,000, or both.⁵

Two limits narrow the reach of this provision. It does not apply to pistols manufactured before the section’s effective date, so owners of older firearms face no liability under it. And replacing a damaged or worn-out microstamping component with a new valid one is expressly lawful, whether for safe operation or for a legitimate sporting purpose.⁵ The tampering ban targets intentional sabotage, not routine maintenance.

How Microstamping Actually Works

Section 27531 defines a microstamping component as a firing pin or other internal part of a semi-automatic pistol that, when installed, produces a microstamp on at least one location of the spent cartridge case each time the gun is fired.⁶ The microstamp itself is a microscopic array of characters that can be used to identify the firearm’s serial number from a spent casing.

In practice, a manufacturer or gunsmith uses precision laser engraving to etch a unique code onto the tip of the firing pin. When the gun fires, the pin strikes the primer with enough force to imprint that code onto the brass. Investigators recovering a spent casing can read the microstamp under magnification and trace it back to the specific firearm.⁷ Even a partial microstamp can generate an investigative lead, in the same way a partial license plate narrows a search.

Where the Legal Challenges Stand

California’s handgun regulations, including microstamping, have drawn Second Amendment challenges in federal court. In Boland v. Bonta, plaintiffs challenged the Unsafe Handgun Act’s chamber load indicator, magazine disconnect, and microstamping mandates that formerly lived in Section 31910. After SB 452 removed the microstamping clause from that section and rebuilt it under Sections 27531 through 27534.2, the state argued that the challenge to the old microstamping requirement became moot because the statute the plaintiffs sued over no longer exists.⁸

The broader litigation continues under the framework the U.S. Supreme Court set out in New York State Rifle & Pistol Association v. Bruen, which requires firearms regulations to be consistent with the historical tradition of firearm regulation in the United States. Whether the new SB 452 framework will face its own separate constitutional challenge remains open, particularly after the January 1, 2028, dealer restriction goes into effect and buyers can point to concrete harm.

1
State of California – Department of Justice – Office of the Attorney General. Microstamping Technological Viability Report 2025
2
State of California – Department of Justice – Office of the Attorney General. Senate Bill (SB) 452 Microstamping
3
California Legislative Information. California Code PEN 27531 – Microstamping Definitions
4
California Legislative Information. California Code PEN 27533 – Microstamping Dealer Restrictions and Exemptions
5
California Legislative Information. California Code PEN 27534 – Tampering with Microstamping
6
State of California – Department of Justice – Office of the Attorney General. Microstamping Technological Viability Report 2025
7
State of California – Department of Justice – Office of the Attorney General. Attorney General Bonta Releases Report, Finds Firearm Microstamping Technology Viable
8
Firearms Research Center. Boland v. Bonta – Appellant Supplemental Brief