Last Tuesday at Philadelphia's Ben Franklin Hall (a more suitable venue is difficult to imagine), British barristers sparred with American lawyers over the legality of the American colonists' Declaration of Independence.
The American's invoked natural law and the consent of the people. "The English had used their own Declaration of Rights to depose James II and these acts were deemed completely lawful and justified." Indeed, self-determination is now reflected in the fundamental rights of the UN Charter.
The British case recalled the historic lawlessness and fecklessness of the secession. "There is no legal principle then or now to allow a group of citizens to establish their own laws because they want to. What if Texas decided today it wanted to secede from the Union?" Denigrating "no taxation without representation" as little more than a wish to avoid paying their due share for the protection of the empire during the French and Indian War, the barristers listed the grievances in the Declaration as "too trivial to justify secession."
I believe it was Gordon Wood, clarifying Jefferson's supposed sufferance of "a long train of abuses and usurpations," who observed that never in the course of human history had men revolted over such slight actual harms. The empty and retreating declaration by the British Parliament that they had the power to rule over the colonies "in all cases whatsoever" was the sort of injury to which the Americans mainly revolted. Abuses of principle. Usurpations of ideas.
Of course, it is the jealous love of these principles and ideas which enabled to new nation to survive and prosper (contrary to the flawed recipe of the French Revolution, for example). Yet these grievances are not the sort for which the U.S. or NATO would now intervene on behalf of a restless people in a foreign land.
The British even slyly invoked the authority of Lincoln as they diminished the authority of "the laws of nature" and, by extension, of "nature's God."
Lincoln made the case against secession and he was right. The Declaration of Independence itself, in the absence of any recognised legal basis, had to appeal to "natural law", an undefined concept, and to "self-evident truths", that is to say truths for which no evidence could be provided.
It is noteworthy that the British attempt to reduce the American argument to a religious dogma. While the spirit of the revolution was democratic and the mode was legalistic, the foundation rested upon a sense of Providence. Interestingly, the British do not seem compelled to address this third leg of the revolution.
There are many compelling and legitimate arguments by which to address the question at hand - and most are well worth serious contemplation.