Sources for info on bans of private sales?

[Monkeyleg]

In a little over a week from now, we're going to have a state senate public committee hearing on a bill--SB104--that would ban private gun sales in Milwaukee county.

I've been trying to find sites that have solid information proving that such bans do or do not work. But I've come up empty.

If anyone knows of a site with information coming from a respectable source, I'd appreciate a link.