I don't think it's possible for them to build in this security in 3d printers since you could print out each piece separately and even when they (who ever they are) can do it, people would bypass it by printing modifications.
And you really expect all manufacturers to stop making arms and every person that has guns to turn them in?
It's not the kind of world we live in. Guns are here to stay how difficult that is to accept for you.
There has never been a time without war and struggle, believe it or not.