Then they would have used the natural right of revolution, which is really what they did anyways. The natural right to revolution is an extra-legal(or illegal in the view of the existing government), an appeal to arms(war) and there is no natural right to win your revolution. Governments, like people, have a natural right to self-defense. The founders knew this and did not expect King George to just let them go. This is why Ben Franklin said; “We must all hang together, or we will, most assuredly, all hang apart.”
Also as moral creatures we can look at the reason(s) why a group of people decide to rebel against their existing government and determine if it was right or wrong. Most assuredly the southern rebels were wrong.
I find it interesting that the Founders were perfectly aware that by rescinding their allegiance to the Crown they knew they were committing treason and could face certain, terrible death. Yet the secessionists and their apologists want us to believe that their action in rejecting their responsibilities as members of the Union and committing criminal acts was somehow not treasonous, not insurrection and perfectly acceptable.
I also find it ironic on a conservative website, which, by definition should be pro-American, see so many people supporting a group that would have destroyed America.