The only thing that prevents us from open carry in public is the crime of Affray, which is to say that a holstered or shouldered firearm carried by a civilian tends to scare some folks as much as if it were being brandished. It is not a real well published law, but I think you will find it is on the books in most jurisdictions these days.

While you'll not find a stronger advocate for effective firearms training, I still have a real issue with attaching qualification to any rights. We have have other rights that I don't think we put such stringent qualification against, though pretty much all our rights are conditioned to some degree (freedom of speech except for slander, libel, or fraud, for instance).