Tennessee is a bit vague on the subject of "under the influence" in regard to carrying.

It's is an offense for a person to possess a handgun while under the influence of alcohol or any controlled substance. But its not specifically defined how under the influence of alcohol is measured as with driving vehicles which is BAC .08.

As far as just consumption of alcohol and gun possession, the only offense i'm aware of is when a person carrying a gun is both in an establishment that serves alcohol and consuming. In a bar and take a sip... an offense.

As far as I know, there is no law limiting self defense to only sober persons or otherwise in lawful possession of a gun. In Knoxville a few years back, a convicted felon in possession of a gun shot and killed an armed robber. Curiously, there weren't even possession charges that Im aware of. The Feds could have done something. I don't know.

The people I surround myself with don't go on stabbing or shooting sprees while having a drink so I'm not that informed on the topic "what if". Cheers..