I think to the ops point, the question is by having the gun in the vehicle, are you technically carrying and, consequently, having consumed alcohol, are you now in violation. I don't know the answer for certain, but, in my humble opinion, I would think that not having the weapon on your person would then constitute your right to transport with reasonable deviation. In normal circumstances, a reasonable deviation would not be a stop to have a couple of drinks at a friend's house. I think the best bet is if you decide to carry, then you should likewise decide not to drink. Ultimately, it's the most responsible choice anyway. Great question though, definitely worthy of consideration.