How valid was the South's justification for secession?
Although the southern states seceded for morally questionable reasons, one could argue that secession was a right that states in the U.S. retained prior to 1868.
Secession had been a hot topic in American political and legal circles even before the Civil War began. The theory of states rights’ seemed to suggest that states, who legally entered into an agreement with the federal government through adopting the constitution, could secede or withdrawal with a similar vote. Political theorists, especially those in the south where the authority of the state was seen as more important than that of the federal government, believed that secession was the right of every state. Southern patriots such as Patrick Henry affirmed that the constitution was an agreement between sovereign states, and that secession was allowed if it was done to safeguard the rights of the people.
There were also many instances were states, both north and south, flirted with the ideas of secession. During the War of 1812, the New England states thought about seceding because the war had ruined their trade with Britain, causing huge reductions in the amount of American exports. During the Nullification Crisis, the state of South Carolina tried to secede over an unpopular tariff.
It wasn’t until after the Civil War in 1868 that the Supreme Court ever ruled on the issue of secession and said unequivocally that secession was unconstitutional. In the case White v. Texas, supreme court justice Salmon P. Chase said that not state, not even Texas, had the right to secede because once a state is admitted to the union, they become a part of an “an indestructible Union, composed of indestructible states.” Basically, the Supreme Court said that no state has ever actually seceded; they’ve only been in states of rebellion.
On a side note, it is interesting to note that today over 22% of Americans believe that states have the right to secede, even today.