Specifically, California requires any handgun sold new in California (with exceptions for law enforcement) to be on a "safe handgun roster" maintained by the state. A handgun must meet certain standards to be placed on this roster. That started out with safety testing, like the requirement that a handgun not fire when dropped, but was later expanded to require features like an indicator that there's a bullet in the chamber.

In 2008, the law was amended to require that semi-automatic handguns stamp identifying marks on shell casings in certain ways that researchers later determined to be more or less impossible. This provision of the law, however, was not to go into effect until the Attorney General of California certified that the technology was commercially available. In 2013, Kamala Harris falsely made that certification and no new model handguns have been added to the roster since. As manufacturers improve their designs, older versions have gone out of production. As a result, the roster has shrunk significantly since.

I wouldn't go as far as to say it's a handgun ban. I think Glock, for example, is perfectly happy to continue to manufacture their Gen3 models as long as the California market exists. But it does lead to a situation where the selection for enthusiasts is extremely limited and will become even more so over time.