There are a number of places here in the US that have bans on air (BB) guns. Even slingshots.
Banning guns simply don't work ... never has, never will. Criminals don't care about laws, that's why they are criminals.
Guns can be home built from scratch or by some off the wall conversions, either is risky as the "gun" may do more harm to the user than the target.
In my generation ... fellas made 'em in shop class (zip guns bieng the most popular name). Of course if they got caught they had some problems coming their way. But hey ... 30+ guys in a shop class with one teacher ... more got out than caught.
Me ... I made a crossbow out of the small leaf spring from a Nash Cosmopolitan and consulted with the shop teacher on the best material for the bolts and the heat treating levels for those bolts. Man that sucker had some power. It'd put a bolt through a concrete block. Got an "A" on that project. My dad on the other hand was less than thrilled. He complemented me on the work. But he pointed out the down side of "over penetration", both relative to hunting as well as general safety. He made a rack for it, hung it on the wall and made the standing rule that I didn't take it out without his knowing it.
The point of the preceding ramble? With even marginal skills you can make a lethal weapon. Be that weapon a gun, a bow, or whatever ... and they can make up all the laws in the universe about not having them and they will still be around. Mostly in the hands of those people that would do harm to you and yours.
:banghead:
:banghead: