California appears to be requiring microstamping technology
The short version appears to be that new handguns will not be added to the list of "acceptable" handguns in California unless they have microstamping technology. Guns already on the list will remain ok unless for some reason they need to be re-registered.
The difference this makes is a significant one. Microstamping is an unproven technology that is easily defeated by means such as changing the firing pin; criminals will not be affected by this requirement. It will increase the cost of new firearms that include microstamping technology and, probably more importantly, block new handgun models that don't use microstamping from being added to California's roster of "allowed" handguns. That means they won't be added at all, unless the California market is deemed large enough to justify the investment by itself.
In short, it's a roundabout gun ban.
There was no need to pass a law to do it, because the law had been passed years ago; all it took to activate this new restriction was a certification that the microstamping technology was available for use.