Technology

PLA is a poor material choice for the application but an easy one. So they might not care. I am not saying that it is dysfunctional, just not a good choice.

PLA hydrolises over time, and becomes brittle and is sensitive to UV, ie day light. It is enough to leave it in a sunny place with some glass reflection for it to soften up and deform but the worst features is probably that unlike many other polymers it tends to fail catastrophically, when it fails, ie nothing much happens until it snaps and splinters. Its impact resistance is also comparably poor.

You seem to run in doors that are open. My whole point was that 3d printing is not suitable to create the functional parts of a fire arm, and by that I mean creating it directly with 3d printing, not some helper products and I also mean for hobbyist levels. Maybe with metal 3d printing etc more is possible but that is neither easy nor cheap nor readily available in anyone's basement. It is easier to get your hands on a CNC and probably cheaper too.

If your argument is that for what 3d printing can be used, it is a fairly easy method and can enable cost effective low number production, yes it can. So yes, if you will, then it has made it more accessible for those things. If someone want to regulate private firearm construction however, just regulate private firearm construction. Don't outlaw open 3d printers, CNCs or if we are at it, woodwork tools.