The Right to Secession

In reading BCOF, I have grappled personally with the question of whether or not any group, Southern Secessionists included, have the right to secede from the Union... then or now.  We look with great bias on the South and say, "No, of course they did not have the right.  They were seceding for the wrong reasons."  Okay.  I can handle that.  They were WRONG.  Wrong about slavery; wrong in general.  But, from their perspective as well as Lincoln's, their right to secede was not found in the Constitution.  McPherson establishes this.  They appeal to a higher law--to the Jeffersonian/Lockean right to revolution.  The government under Lincoln was not going to secure their property, they feared.  From the perspective of the South, the federal gov't was becoming "destructive of these ends."  So, clearly, the right to revolt/secede is a subjective thing.  Certainly from the British perspective, the Americans of 1776 did not have the right to "secede" from Britain either.  See THIS ARTICLE.
So, under what conditions does anyone have the right to secession/revolution?  Since I view this as such a subjective question which cannot be answered outside of a specific context or situation, I ask it rhetorically.  Had I lived during the Secession Crisis, or if any group tried to secede today, I honestly feel that I would probably feel inclined to just say, "fine, go."  McPherson discusses that there were was a minority that felt similarly during the crisis of 1860-61, but that they did not carry much weight.  So many politicians and individuals were so invested in the issues of the time (emotionally, economically, politically, etc.) that they could not just let the South go.  Additionally, McPherson presents the arguments of some Northerners which imagined a nation in which secession would not be challenged... anyone and everyone would secede instantaneously if they felt wronged.
Bottom line, these are tough questions.  Let me know if you have the answers!