Madison dicussed governmental powers and the differences between those for the federal government, and those reserved to the states:
"The powers delegated by the proposed Constitution to the federal government are few and defined. Those which are to remain with the state governments and numerous and indefinite. The former will be exercised principally on external object, as war, peace, negotiation, and foreign commerce; with which last the power of taxation will, for the most part be connected. The powers reserved to the several states will extend to all the objects which, in the ordinary course of affairs, concern the lives, liberties, and properties of the people, and the internal order, improvement, and prosperity of the state." (Federalist 45).
The powers reserved to the states have to do with localized control within a federal system. Unilateral secession purports to abandon that system and deny the citizens of their Constitutional rights and protections. Unilateral secession is not, therefore, a constitutional process, and is not authorized by the 10th Amendment.
The Tenth Amendment, as an article of amendment, need not conform to anything in the foregoing articles and clauses, which were Madison's subject in Federalist 45. The amendment changes the document, and the social compact. That is the significance of the Tenth Amendment: it is completely transformational.
Notwithstanding the post-Lincolnian Imperial State's propaganda minimizing the Tenth, the Amendment has not been repealed, but only violated in gross terms by open warfare.
And, for the last time, all powers are reserved to the States which are not explicitly granted to the federal government under the terms of the Constitution. That is the criterion for discerning whether the People or the State possess a reserved power.
Unilateral secession purports to abandon that system and deny the citizens of their Constitutional rights and protections.
The problem with abstracting an action and making it the subject of a sentence, the object of which is the real agent of the action, is that it is inherently confusing. The citizens, the People, seceded. They walked away from the Constitution, and wrote themselves another. Your pretense that "someone done them wrong" and that somehow, an unspecified Somebody did something wicked to the citizens, is simply absurd here.
Apparently they do not understand what federalism means and reject the authority of those who do: Hamilton and Madison.