As of 5/17/2013, looks like California is officially requiring microstamping on all new semi-auto firearms. No stamp, not legal in Cali. Read the memo at oag.ca.gov:
In 2007, Assembly Bill 1471 was passed and signed into law, requiring all semiautomatic pistols
to be equipped with microstamping technology—“a microscopic array of characters that identify
the make, model, and serial number of the pistol, etched or otherwise imprinted in two or more
places on the interior surface or internal working parts of the pistol, and that are transferred by
imprinting on each cartridge case when the firearm is fired.” (Pen. Code, § 31910, subd.
(b)(7)(A).) The legislation further provided that this requirement becomes effective when the
Department of Justice “certifies that the technology used to create the [microstamp] imprint is
available to more than one manufacturer unencumbered by any patent restrictions.” (Ibid.)
Certification of the Microstamping Technology
On May 17, 2013, the Department of Justice issued a certification that the microstamping
technology is available to more than one manufacturer unencumbered by any patent restrictions.
A copy of the certification is attached to this bulletin.