Ask HN: What's the Deal with Plastic Guns?

So there are these plastic guns that are lethal within a couple feet and you can ship over state lines. They only cost a couple hundred dollars. What's preventing people from buying several every time they get a paycheck and then mailing them to all the people in the city they live in and dislike? As far as I know it's legal.

Is this a paradox? It feels like a paradox somehow? Paradox. There I said it again. Paradox. Oooh...paradox.