Not really. As just a simple example when the president of the CSA was captured Davis wasn’t formally charged with anything. He wanted his day in court, and wanted the Federal Government to prove what he had done was illegal. I believe the Successionists were fundamentally wrong about a lot, but I believe their legal case was pretty solid.
Right, but after expulsion, it’s no longer a state.
Besides, if there’s a broad consensus in Congress and the states that some state should be expelled, the Constitution could just be amended.
Not really. It was a political not a legal decision. They could have tried Davis and other Confederate leaders and they would have been found guilty. But what would it have accomplished? It’s not like they were going to try a second time. So the government decided not to prosecute them.
Please fight my ignorance then, which law did he break?
I really don’t know.
Yes. If Delaware want to become a Most Serene Principality or New York wants to become a People’s Republic, I won’t hinder them.
Because country and city governments are creations of the state government, whereas state governments are not creations of the federal government.
The colonies may have been part of the British Empire, but were never part of the United Kingdom. If they had been, they would have been represented in Parliament.
The southern states, OTOH, were full partners in the U.S.
So, if the Colonies had been part of it, with representation and everything, you would consider Washington et al criminals and find their action objectionable?
More so, definitely.
So when the Continental Congress rejected the offer of virtual representation from the British Parliament, you are saying that they were in the wrong? That they should have accepted?
No, because virtual representation wasn’t the same thing as actual representation. Hence the term, “virtual representation”.
Legally speaking ? I have no idea how any of that crap works, don’t ask me.
Morally speaking ? The right of people to dispose of themselves (i.e. self-determination) is one of the more fundamental ones. So yes, absolutely, provided a majority of people in a given State want out, they *should *be let out peacefully.
It was a step up in the right direction, though. And it was absolutely rejected. You think that was wrong?
What if the minority of people in a state what to split part of the state off?
I disagree that it was a step in the right direction. So no.
Let 'em, long as they can muster a local majority.
Sure. Southern states also had conveniently traced lines on what was rightful and what wasn’t. So would any hypothetical seceding state.
Well, simple majority would be too slight a margin to be any stable, say an 70/30 split or better.
Well, sure, if you want to go full relativist then I guess everything’s cool.
I don’t. I’m accusing you of being one. The point I’m making is absolutist: either you consider that the US had a right to secede, and therefore any seceding nation has a right to follow the same path, or you don’t. You are the one with the moving goalposts here.
Basically, any nation has the right to secede as long as they win the conflict that results 
This is one of the more crucial considerations to secession. What does a state become once it has seceded? The US would not be obligated to recognize the sovereignty of the seceded real estate unless (presumably) a previous arrangement had been reached prior to secession. Otherwise, a state that secedes just becomes some land with some people on it who claim to be citizens of Newhatever. If the process is not handled with due care, adjacent states might begin to summarily gobble up edges of Newhatever (perhaps with those residents’ consent or behest) while the larger nation looks on with indifference or tacit approval.
An existing state is ipso facto due fair courtesy and respect from the larger nation. A seceded state is just some vague entity, if even that, that used to be a state. Hence, to keep things from getting chaotic, the secession process must needs be rather arduous (though I am not convinced that a constitutional amendment would be required, since admission to the union did not require one). Given adequate difficulty in getting the hell out, one might imagine that the residents and local government would be inclined to at least attempt the less perilous approach and try to work out a way to remain in the union (like – gasp – a compromise).