Hm.. then the ones left holding the guns would be the ones who refuse the law, ie. the criminals, who now have a sheep hunting fest on the disarmed civilians. Not to speak of black markets, like in USA alcohol ban before the first New Deal with Roosevelt.
The whole gun debate thing is messy and depends on country culture and situation. I don't think a world consensus exists, in some countries gun ownership makes sense, in others it doesn't. That's how I see it.