See Article I §8 for the enumerated powers. Invading a state to force it remain in the union is not one of them, the use of force against a state was voted down twice in convention.
The powers not delegated to the United States by the Constitution, nor prohibited by it to the states, are reserved to the states respectively, or to the people.
See Article I §10 for the powers prohibited to the states. Secession is not prohibited. The founders just dissolved a perpetual union, and did not write such into this one.
The states met in convention (as required in a republican form of government), the people of each seceding state exercised their sovereign right to adopt a form of government that suits them best (see the Declaration of Independence). Per the Constitution's Full Faith and Credit clause, each state in American union was required to acknowledge the validity of the acts - even today New York cannot adjudge that a Georgia Act is illegal.
The states, as required, assembled and withdrew their ratifications, resuming their delegated powers from the union, and resumed their place among the governments of the world. The Supreme Court acknowledged the right of each state to leave in Penhallow v Doane's Administrators , 3 Dall. 54 (1795).
After secession, the several seceded states assembled as did their forefathers, in convention, to form a new Confederation. Before, during and after that convention the states independently, and the Confederate government sent emissaries to Washington to renumerate the union government for any and all properties, to discuss economic treaties, and the ensure that the Mississippi would remain open to federal traffic. Lincoln and Seward lied on every attempt, in particular to Justice Campbell, breaking the existing armistice, and sending armed troops into Confederate waters.
I guess you side with the Tories, and against the American colonies in the secession from Great Britain. Against the Declaration of Independence as well.
False. Guess you side with total anarchy. As is your interpretation of the Constituion. Sorry, but there it is. Your position is just untenable. The Convention they purposed to have, in fact, was totally defective. They could not secede from the government under the same procedure that the government had been created by. They needed the whole of the country. No "rump caucus" could effectuate any secession constitutionally. Secession can only happen by agreement, or there never was any union in the first place. The war for indepence was with 13 colonies declaring State sovereignty...that they had never had before. And it was done only with huge burdens of proof that the government was intolerable. As Jefferson said in the Declaration, Not for Light and Transient Causes.
The Slave states could not make any similar claims in their asserted (and basically phony) grievances. Secession is not at will. And most of the slave states were never sovereign, having been created by the national government's polity...which clearly retained sovereignty...and had been the entity which financed and protected these new territories and states. Absconding by a rump convention that no constitutional scholar would recognize as legitimate, and running with the money, so to speak, as if there is no debt owed, is just thievery.
BTW: Even following your position, let's say the Slave States successfully effectuated their secession legally...there is then NO LEGAL defense for the U.S.A. to then simply....DECLARE WAR ON A HOSTILE STATE. Which manifestly, the South was. You can still look at it that way...and guess who won. Get over it.