In TN, i'm pretty sure that if you and someone else are drunk, and you let them drive your car and you are with them, you both get a DUI.
What I don't know is... what if you aren't drunk? I'm GUESSING you'd still get a DUI if you are with them and know they are drunk.
What if you don't know they are drunk? No idea...
What if you aren't with them, but handed them the keys while drunk? No idea...