Who supported the principle of states rights?

Answer 1

It's a tricky question. The answer depends on who you ask and where their sympathies lay. Technically both sides supported the concept; but each side had different views on how it should work. Additionally, both sides argued against it in certain ways.

The South is generally considered, particularly by Southern sympathizers trying to rationalize the rebellion (that is, they don't want to admit that slavery was the actual cause of whole Civil War mess), to have strongly supported the concept. They argued that states had the right to leave the Union at any time for any reason. However, they also disliked Northern states passing laws against slavery within their own borders, or even that some Northern states were granting civil rights to black people. When they did secede and write their own constitution, they made a point of eliminating some states rights (mainly as pertained to slavery)- which is a little hypocritical.

However the North also argued in favor of the concept. They claimed that things like the Dred Scott decision and the Fugitive Slave Act were violations of the the rights of Free States. They also pointed out the South's inconsistency in applying states rights, as noted above. But the North disagreed with the South that states had the right to leave the Union- they believed the Union was meant to be "perpetual", as stated in the Articles of Confederation.

The truth of the matter is that both argued for states rights, but viewed them in different ways and applied their arguments inconsistently when it was convenient to them.