One miscue in that department:
An older man approached his bank and observed a bank robbery taking place. He went back to his car and retrieved a .357 Magnum revolver, and shot the robber as he was approaching this man, apparently with the idea of carjacking. Memphis police detained the citizen, but he was released wiothout charges.
But, a few days later he was arrested by Federal officers. Appears he was a convicted felon in possession of a firearm.
Unfortunately, some drug dealers slip through on the "self defense" clause. Until they are convicted on drug possession charges, they are as pure as the snow.