The SF Chronicle’s Bob Egelko posted this, which has a few more details. I’m still trying to figure out exactly which patent this is. It sounds from the article like it’s the Lizotte patent. As far as I know, that patent is still in force and thus the technology cannot be called “unencumbered” as the law requires.

Chuck Michel told the Chronicle:

“This is not going to help solve crimes,” he said. “It’s easily defeated, easily wears out and can be used to lead police down false alleys” if the serial numbers are altered.

Worse yet, Michel said, manufacturers will be unwilling to add this expensive feature to guns sold in a single state, and will instead keep manufacturing weapons for the other states, where demand already far exceeds supply. The effect, he said, would be a ban on new semiautomatic handguns in California, which the NRA will challenge in court.

There is also the possibility that gun makers will stop manufacturing guns for California out of liability concerns. The marking technology mars the cartridge case during the firearm’s discharge cycle. Specifically, the technology imparts two marks on the case; one on the primer and one on the case wall. These are both structures that contain pressure as the cartridge is fired. These are normally smooth, continuous surfaces which even distribute forces throughout the case. Any marks impressed into the primer or the case wall must be irregular in nature or they won’t carry any information. And since they are irregular, they must cause an irregular distribution of forces. This can lead to a failure of the case wall or the primer. At the very least, the marking surfaces along the side of the case wall will become fouled with brass shavings, torn loose as each marked case is extracted.

Yet another requirement of the “not unsafe” gun law in California is that new designs must be submitted for testing to an approved lab. Among the required tests is a 600 round series of test firings…

31905.  (a) As used in this part, "firing requirement for handguns"
means a test in which the manufacturer provides three handguns of the
make and model for which certification is sought to an independent
testing laboratory certified by the Attorney General pursuant to
Section 32010. These handguns may not be refined or modified in any
way from those that would be made available for retail sale if
certification is granted. The magazines of a tested pistol shall be
identical to those that would be provided with the pistol to a retail
customer.
   (b) The test shall be conducted as follows:
   (1) The laboratory shall fire 600 rounds from each gun, stopping
after each series of 50 rounds has been fired for 5 to 10 minutes to
allow the weapon to cool, stopping after each series of 100 rounds
has been fired to tighten any loose screws and clean the gun in
accordance with the manufacturer's instructions, and stopping as
needed to refill the empty magazine or cylinder to capacity before
continuing.
   (2) The ammunition used shall be of the type recommended by the
handgun manufacturer in the user manual, or if none is recommended,
any standard ammunition of the correct caliber in new condition that
is commercially available.
   (c) A handgun shall pass this test if each of the three test guns
meets both of the following:
   (1) Fires the first 20 rounds without a malfunction that is not
due to ammunition that fails to detonate.
   (2) Fires the full 600 rounds with no more than six malfunctions
that are not due to ammunition that fails to detonate and without any
crack or breakage of an operating part of the handgun that increases
the risk of injury to the user.
   (d) If a pistol or revolver fails the requirements of either
paragraph (1) or (2) of subdivision (c) due to ammunition that fails
to detonate, the pistol or revolver shall be retested from the
beginning of the "firing requirement for handguns" test. A new model
of the pistol or revolver that failed due to ammunition that fails to
detonate may be submitted for the test to replace the pistol or
revolver that failed.
   (e) As used in this section, "malfunction" means a failure to
properly feed, fire, or eject a round, or failure of a pistol to
accept or eject the magazine, or failure of a pistol's slide to
remain open after the magazine has been expended.

I cannot help but wonder if a microstamping-compliant gun will be able to fire 600 times without “a failure to properly feed, fire, or eject a round“. As mentioned above, the case wall marking surfaces will become fouled with brass as each successive round is fired. This fouling could cause the gun to fail to cycle. This would cause the gun to be labeled as “unsafe” per 31905(e). Furthermore, the gun may be called “unsafe” if the markings fail to take due to the fouling. This would fail the gun under 31910(b)(7)(A).

At least two possible failure mechanisms during test, potential product liability lawsuits… Yeah, I can just see manufacturers lining up for that.