"Slavery, state's rights, tariffs, etc. were the issues that brought about secession, not the war. There is no constitutional concept of a perpetual or indissoluble union. The Constitution was a contract (not a binding one, mind you) between the member states, which retained the right to withdraw at their discretion. A state that could voluntarily accede could voluntarily secede. (To this day, I will not say "one nation indivisible" when pledging the U.S. flag.
-- Brian, Rome, Ga, USA" and

"The war had NOTHING to do with slavery. Slavery was brought into the mix by Lincoln to keep Europe out of the fight. England and France were siding with the south. They had already ended slavery, and when Lincoln made it about slavery, they could not step in and side they the CSA any more without the obvious hypocrisy. The emancipation proclamation was a joke. It freed no one. The Declaration of Independence alone gives states the president to secede from the VOLUNTARY union.
-- Rick, Safety Harbor"
are both completely right!