A poster said earlier that this is one reason why concealed is better than open. I agree.
Anyway, the saying goes that when it comes to the law, ignorance is no defence. Slightly harsh IMO, but there it is. For something as potentially contentious as carrying a gun (or rather being seen to be carrying a gun), I think when there is a change in the law, there should be some public awareness carried out.
At the very least something like leaflets in gun stores for people to read. It should outline what the new law will mean, in layman's terms. Also for any CCW course, it seems a good idea to also educate applicants on some of the "diplomacy" or soft-skills that really should go hand in hand with gun carrying.
By that I mean that the hot-head who is usually ready to mouth off, should realise now that doing so with a gun on the hip could escalate things to a place they'd rather not go, whereas without a gun, they might have just earned themselves a thick lip...
In the case of the story above it seems like there was a gun owner who simply did not understand to where his mandate extended, and overstepped the mark. Hat's off to the other who kept his cool....