Good thing Washington, Jefferson and the others didn't know that.
As for whether or not secession is legitimate under the US Constitution or not, that question became moot once the constition al promises of limited government were abrogated and trampled underfoot.
The founding fathers would most certainly not recognize today's government as resembling anything they had intended to govern the America they founded.
It's downright unAmerican. It's ironic, though, that the war fought in the 1770s was really the First American War of Secession, since they did not intend to bring about a regime change in England or Great Britain, only establish a self-government for the former colonies. That attempted by the Confederacy was the second, and was most certainly neither a *civil war* nor a *war between the states.*
I suspect that we'll see a breakup of the USA similar to that of the Soviet Union, possibly within my lifetime.
That may constitute the Third.
-archy-/-
Playing with words. What occurred in America was a Revolution against rule by King. What occurred in 1860s was rebellion against legitimate government duly elected. The proper place for disputes between states in our system is the Congress, or in the end, the courts.
If all of that fails, the last resort is revolution. There is no inbetween. No peaceful secession. It doesn't exist. The southern states chose to rebel, and are judged by history.