No, certain guns shouldn't be sold in the first place anyway... I don't see any other use for handguns, other than shooting other people. In defence, or anger. Much like buying a memory card, with a hack for breaking copyright laws (please don't speel some BS about using it only as a memory card,) is enabling you to plagiarise other people's work.
Granted, the consequences are massively different. Taking someone's life is infinitely worse than stealing someone's work. So maybe this analogy isn't perfect, but the moral principles are the same.
Take, for example, a drug dealer. A drug dealer doesn't necessarily use any of his/her own drugs, Likewise, when the dealer sells those drugs to a client, he isn't necessarily forcing the client to take the drugs, also, the client isn't necessarily buying the drugs to ingest, maybe the client just wants to use them for scientific purposes...
So why then, are there laws to stop the dealer, and the client, from doing trade? Because they are dealing with a substance, that's most likely function is to consume, which is illegal.
When a retailer sells an item, that's main function is to break copyright laws (again, don't tell me it's primary function is to store personal files, because that's BS,) Why is this any different, morally?
Again, the consequences of these examples are massively different, but if you want to live in a morally balanced country, you can't be such a massive hypocrite. Stealing is morally wrong, enabling someone to steal, and then claiming ignorance, is just plain stupid.