There are several snarky knee-jerk reactions in the comments here, but state assemblies pass things all the time that ultimately fail to pass or get vetoed. Now the public will debate it, contact their state senators to give their opinions...it's all part of the process.
A law like this just passed in New York State.
If this fails it'll be because the tech industry expresses disapproval too loudly to ignore.
The legislators don't care about the underlying criticism. Almost no legislators have ever used a 3d printer or written any software, beyond maybe simple assigned programs if they had a required intro-to-programming course. Few are "tech" people. The rest don't understand this technology, or any technology really, beyond it being a black box for specific purposes. They see 3d printing and plastic guns and think something must be done, because the 3d printing black boxes are producing dangerous weapons.
California constantly passes all kinds of weird, pointless, and burdensome gun laws. There are so many of them, and they're so poorly written, that no lawyer in the state who can confidently tell you what's legal and what isn't until a court chimes in. There's no meaningful process around any of that.
The only thing that's different about this one is that it mentions a technology geeks care about. But I doubt that's enough. As another commenter noted, you can no longer hide behind "we have no technology to distinguish between guns and non-guns". We have AI that's supposedly PhD-level and will soon automate all jobs. Looking at STL files sounds like a job.
That's actually one of my fears about LLMs: they make thought policing cheap. There are profound privacy and cost barriers to having a Facebook employee review all your private messages. There are no such barriers to having a robot watch all your IMs in real time.