Tell us the truth about what happened.
I suspect the truth will be wasted on you but here goes. And I'll reference a nice, neutral source - Ohio History Central
To begin with, Vallandigham was not a congressman when arrested, he was an ex-congressman having been defeated for re-election in 1862. He was not arrested on Lincoln's orders, he was arrested on the orders of Ambrose Burnside, Commander of the Department of the Ohio, for violation of General Order 38 that Burnside had issued in April 1863. It was that general order, and not any order of Lincoln's, that made declaring sympathy for the Confederate cause punishable by jail, expulsion, or even death. It was a military tribunal which convicted Vallandigham and sentenced him to prison for the duration of the war. Lincoln's sole part in this was commuting Vallandigham's sentence to deportation to the Confederate States. It's interesting to note that Vallandigham's time in the Confederacy lasted only long enough to be put on a blockade runner leaving the country; some accounts say he was under armed guard the whole time. In any case he was back in Ohio within a few months.
And the legal basis for this is what? Is there precedent for this? Has this ever happened since then? Would the courts accept these arguments now?
Wait, what? Deportation? Isn't that tacitly acknowledging them as a foreign country? You cannot "deport" someone to the same country. And what is the precedent for deporting someone who is an actual US citizen?
On the other hand, if Lincoln regarded them as US states in a condition of rebellion, is this not akin to tossing someone to a dangerous mob?
What is the legal basis for doing that? How is this legal any sort of way?