> but why in USA people try to regulate 3D printing instead of banning sale of bullets without a firearm owner license

I mean we're talking about CA, so they kinda already tried to do that

https://giffords.org/lawcenter/state-laws/ammunition-regulat...

But, it may not be constitutional:

https://calmatters.org/justice/2025/07/gun-law-ammunition-ba...

So the real reason is that the ultimate law on the books on gun regulation was written by a band of, you know, armed revolutionaries, who were pretty big fans of the whole armed revolution-ing thing. And it still hasn't been amended.

I bet if you went with a simple majority vote today, you wouldn't get the 2nd amendment. But amendments are pretty difficult to pass, much higher requirements than a simple majority.