Yet the Constitution delegates power to the President as Commander-in-Chief of all of the States and he takes an oath to defend the Constitution (the law) of all of the States and to defend all United States citizens from rebellion, invasion or an attack on our Constitution.
I would say that it pretty well outlined that the President was not simply a figure head for a treaty among the States but the leader of all of its people empowered with the duty to defend the Constitution and all people of the United States.
Under your ideal though a simple majority of a state could enslave people and rebel against the Constitution without any due process at all to its people or the people of other states and wage war against the United States legally. Yet there is no portion of the Constitution that makes the actions of democrat rebels to do so legal at all. It is all just hyberbole and not backed up by the Constitution at all.
The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people.
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Amendment X
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.
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Read it and weep...
;>)