You missed Madison’s point. When we’re dealing with constitutional compacts between separate political bodies into a federated constitutional state, secession IS the expression of the natural right of revolution. It’s the way that one of the individual political bodies that acceded to the union has of dissolving that union and going its separate way, through a revolution against the union. Secession IS revolution, and is justifiable under “intolerable oppressions”.
It’s true - the old order is NOT under an obligation accept the new. Great Britain was within its rights to oppose the departure of her American colonies, and the North was within its rights to try to stop the South. Remember, I’ve consistently been saying on here that I don’t think the South should have won (would have been very, very bad for future world events), but instead that all States, Southern or otherwise, DO have a right to secession from the union if they choose to exercise it for solemn purposes.
And you apparently miss the overall point of Madison's letter, which is to address "the question whether the Constitution of the U.S. was formed by the people or by the States, now under a theoretic discussion by animated partizans." And Madison comes down, for the most part, on the side of "the people," saying:
"the undisputed fact is, that the Constitution was made by the people, but as imbodied into the several states, who were parties to it and therefore made by the States in their highest authoritative capacity. "In short, the Constitution is not an association of states, but an association of the people, who are simply organized by state.
Secession IS revolution, and is justifiable under intolerable oppressions.
Indeed. But in this you are in a different place, than, say, Jefferson Davis, who said, in his first inaugural,
By virtue of this authority, the time and occasion requiring them to exercise it having arrived, the sovereign States here represented have seceded from that Union, and it is a gross abuse of language to denominate the act rebellion or revolution