Once again another proposed law that would just make normal people's lives more difficult while doing nothing to prevent individuals who are motivated to do the illegal thing from doing it. Offline 3D printers are really not difficult to build, there are many open source plans and all of the hardware is available to order from AliExpress making it simple to do. Somewhat more technically capable people can cobble them together from alternative sources if they don't want to purchase things online.

But the bar is even lower than that since you can simply buy a gun much more easily than you could 3D print parts for one.