I just want to say that I respect all of the opinions that have been put forth in this thread concerning States having the right (or not) to secede. There is so much historical information to study about the subject that it would take quite some time to go through it all.
It is certainly true that believing that States SHOULD have the right to secede is very different than saying that according to the Constitution, the States DO have the right to secede. Even though I am still unsure about the constitutionality of secession, I am very much in favor of states having the right to secede.
The reason I say this is because if we were to say that a State NEVER has the option of seceding, then we essentially grant potentially unlimited power to the Federal Government. If the Federal Government were to do something that was both immoral and unconsitutional, a State could never do anything more than cry out and complain. It could not secede, and it could not resist.
Consider for a moment an example where the Federal Government 'crosses the line' against a State Government. It very well might be possible that one day the Federal Government decides that ALL states MUST recognize ALL same-sex marriages. Now, in this situation a state would have to comply, and could do nothing more than complain about what the Federal Government has done.
Please understand that I am not saying that a state SHOULD secede if the Federal Government tries to redefine marriage nationally. What I am saying is that I believe it is very possible that the Federal Government could 'cross the line' to the point that a State could be justified in seceding from the Union. That is why I believe that States SHOULD have the right to secede. I honestly do not know what situation would need to develop in order for a State to be justified in seceding, but I do believe that there is 'a line' out there that the Federal Government might one day cross. To say that a state does not have the right to secede is to essentially say that there IS NO LINE that the Federal Government could cross. It is to say that the Federal Government COULD potentially have unlimited power over the states (if it chose to do so).
On a more personal note, I honestly do not know what I would do if the Federal Government ordered me to launch air strikes against my home state of Pennsylvania. There are Air Force pilots that I have flown with that openly declare that they would fight for their state if it were to secede from the Union. I pray that there will never come a time where Washington D. C. orders me to bomb members of the Pennsylvanian National Guard (which my cousin is a Captain in). If such an order were to come down, I do not think I could follow it.
Perhaps this is what motivated many Confederate soldiers to stand against the Federal Government. There can be no doubt that many of them were appalled at the idea of going to war against their own countrymen, to invade and subdue their own states. Regardless of whether or not we can 'prove' that secession was unconstitutional, there is no doubt that millions of Americans in 1861 thought that it was a perfectly legitimate option. Perhaps they were all wrong in their interpretation of the constitution, but I still have not been fully convinced that secession is wholly unconstitutional. There is no doubt that the idea of secession was thrown around during the Hartford Convention of 1814 (as well as the War of 1812). Whether anyone was serious about it or not is a different question. Yet even if it could be shown to be clearly unconstitutional, I still believe that States SHOULD have the option to secede as a last resort against a potentially immoral and tyrannical Federal Government.