No state had, nor do they have today, the Constutional right to secede from the Union as of 1788, which was when the Constitution became law. The Constitution spells out the powers and responsibilities of both the federal government and states. For example, states cannot declare war or coin money or do many other things that would be precipitated by an act of secession. Section ten specifically says that no state shall enter into a confederation, which is exactly what South Carolina, Alabama, Mississippi, Florida, Georgia, Louisianna, Texas, and South Carolina did, and this was why the civil war was fought. Check it out, section 10 of the US constitution: "No state shall enter into any ... confederation." Any dissolution of states from the union immediately obviates the United States, which is what Lincoln fought to preserve. The issue started out as one over slavery, but became one over secession in 1860 when those southern states left the union after having lost a fair election.