If a few countries can sue Valve so hard they got rid of CS:GO gambling lootboxes, then I'd be willing to bet they can do the same to this cockend. Hell, they could prolly do it even more easily, since I somehow doubt that he has Valve's standing army of lawyers and exceptionally deep pockets.
Well, they can do that, but the genie's out of the bottle now. (Really it was when Wilson first posted this stuff online, and even though he got slapped with export controls because he did it in a high-profile way, the article notes that there are others who have just stayed quieter about it.) Wilson's intent, as near as I can tell, was to make effective gun control, anywhere, next to impossible, and whatever happens after this, he's probably succeeded. It's not like loot boxes where you can ban them; no country or group thereof is going to be able to keep these blueprints from circulating.
Another thing to add to the list of reasons why the rest of the world might have a case for invading and conquering the US (climate change denial being chief among them).
If the gun is meant to be fired more than once it will have a metal barrel that can be detected. If it uses conventional ammo it can be detected though being small it is easier to smuggle. You could bring powder and lead balls and then use matches or repurposed electric wires and batteries to detonate it but at that point you are going through so much trouble for one or two shots that you might as well build a bomb in your underwear or something and be more effective in whatever you are trying to do.
Sometimes all you need is a few shots. It probably isn't anywhere close yet to enabling even something like Columbine (yeah, that's how small Columbine was compared to what we see today with the massacres in Norway, Las Vegas, or Orlando), though apparently there are blueprints for an AR-15-like weapon, but for random havoc and panic, or a targeted murder (jilted lover perhaps), one shot per gun might be all you need, and even if you abandon the gun(s) at the scene, as long as you've been careful in your handling, there's no way to trace it to you--that's what really makes this dangerous for gun control efforts.
And Wilson said that that's what he wanted to do--kill the revitalized gun control movement in the US that we see gaining strength after Parkland by making "common sense gun control" impossible, which will incidentally also have the effect of making every other country's gun control laws basically impossible to enforce.
Basically, your right to life (Art. 3, Universal Declaration of Human Rights) is less important than everyone's "right" to have untraceable, possibly undetectable, guns (not found in any such document except for a misinterpreted provision in the world's most outdated Constitution).