The Declaration of Independence may say that but is it in the Constitution of the United States of America?
The Declaration was settled by arms against the British Crown.
If one of the states wants to secede, let them draft their own Declaration and see if the fedgov lets them go.
It was tried once and failed. I wouldn't bet it would succeed now.
I tend to disagree. There was a galvanizing moral issue in the War Between the States that motivated northerners to fight hard against southern independence. There is no such issue today. Can you really imagine Washington and the American people generally fighting with the kind of sacrifices seen in the 1860's or 1940's to keep a conservative breakaway South Carolina (i.e, the Exodus project), or a hispanicized Arizona, in the Union?
I can't see it. I think if conservatives really did pull off an exodus to a state like S.C. and made it clear that they would fight tooth and nail, Washington would be forced to blink. Liberals would say 'let them go' not 'let's suffer a million casualties to keep them'.
Looking at history (Roman empire, etc.), I get the impression the way these things work without the central government crushing the insurrection is when the central government no longer has the strength to hold the states together, then they can split away from the central government.
Then there is the small matter of the individual states now on their own having to defend themselves against their neighbors once they are on their own.
I see it is the "cycles of civilization" theory that I read somewhere. It says that all societies go through the stages of (paraphrasing and simplifying here) Creation (struggle to make something), Complacency (relax when you have it made), Chaos (differences start to cause rifts in society), and Collapse (system falls apart due to lack of wealth vs demands or violence between groups within or from outside invaders).
The Collapse stage is kind of messy though...
As you well know the Constitution is silent on the matter of secession however, the 10th Amendment reserves all rights not specifically granted to the federal government to the states. Therefore the federal government has no legal or constitutional power to prevent a state from leaving the union. Personally, there are a few that I would like to see secede; Mass, Conn, RI, NY, NJ, MD, CA, to name a few.