“WHatever mistakes Lincoln made, I’d much rather be a Copperhead in the North than a Unionist in the South.”
It was military courts all around.
From what I've read they didn't often bother with courts in the Confederacy. A bullet in the back or a trip (often one way) without trial to the reb gulag in Tuscaloosa was the frequent fate of those Unionists whose property caught the greedy eyes of the local authorities.
For the victims, I'm sure it was scant comfort to know that their abuse was at the hand of fellow southerners undertaken in the name of states' rights.