After decades of stupidity, TN got it right recently.
Here in TN, you can carry your gun anywhere that is not posted private property or certain government buildings. If you drink even 1 sip, you broke the law. You can go into the bar, but you can't drink -- which FINALLY allows us to get a steak while carrying instead of just fast food as good eating places are all considered "bars". Basically you choose .. drink, or carry. On top of that, you can't be prosecuted for legitimate proven self defense if you broke other firearms related laws in the process (for the most part, and I THINK this includes drinking. It does not, as I recall, include being a felon though).
But it varies from state to state. IMHO being at 1/2 the driving limit or worse should be at least a misdemeanor if armed. Booze and guns don't mix, and we don't need drunks giving carry permit holders a bad name.