Look Non, as they say, they'd already let the cat out and you can't put its crap back in. You declare secession constitutional in 1869, can you imagine what would have happened by 1870? With the 14th Amendment fiasco, I'm of a mind Oregon and New Jersey would have joined up with the Southern states, or heck started their own union. As for Milligan, lincoln was already dead, who cared what folks thought about him? Let's throw him to the wolves because what he did was really wrong when you look at it. And it was only part of his whole plan. But secession, ah, secession, we can't say that's legal because then EVERYTHING lincoln did, and some of us could easily be considered co-conspirators (Chase in particular), we better let that dog alone because we don't want to be arrested on charges and destroy a union which cost 600,000 men their lives
a) deny the humanity and general tendency of man to act towards own self gain
b) deny the fact that at this time every other official tied to any government organization was so deep into kickbacks and getting the most for themselves wasn't happening
c) that these men were above reproach and that they would in no way be influenced from their surrounding culture and the war they had just been through
These men were no angels, just as Davis, Jackson, and Lee were not. In the end however, the Confederacy had precendence from previous actions of the north and the Constitution on its side. These men just made it up, much as their appointer had done