Sugarfoot Jack-The sign you saw was a response to a situation a few years ago where a number of gun rights advocates began carrying their weapons to restaurants and such places to "educate" the public on their right to carry arms under Virginia Law. Here's an article: Gun Toting in Virginia

It was determined that the owners and operators of any establishment had the right to prohibit this sort of thing, so, as a response, a number of places posted signs, which are still up, though, since the Virginia Tech shootings, no one has really been making a show of their gun rights.