3d printing guns was never illegal. This was a first amendment case about distributing gun plans/files. Before and after you are allowed to manufacture any gun that you may legally own already. If guns are prohibited to you or in your state it is just as illegal to print one as it would be to make one from black pipe. If you are allowed to own a gun you can already make as many as you like. If you want to sell them you need a manufacturers permit.

And don't forget, none of these use 3d printed ammunition, you still need to get bullets.

you can buy a desktop milling machine capable of finishing 80% lowers from Defense Distributed already, that is much better than a plastic gun.

https://ghostgunner.net/collections/featured-products/products/ghost-gunner-2-deposit