When the original states ratified the Constitution, and when later states petitioned to be admitted, they all agreed to abide by the Constitution and that the Constitution trumped their state Constitutions and local laws when there was a difference between the two. Since the southern acts of unilateral secession were ruled to be in violation of the Constitution then their actions were illegal.
The New England states certainly didn't think it was "perpetual" or they wouldn't have come within a gnat's hair of seceding themselves a few decades after the Constitution was ratified. (more than once)
But unlike the southern states the New England states didn't enter into a rebellion. If they had I would have expected the governments reaction in 1814 to be the same as it was in 1861.
You are aptly named. The legality or illegality of secession has absolutely nothing to do with the issue of Wlat's false statement regarding the unity of the framer's understanding, which you appear to be supporting. I was not arguing for the legality of secession. I was only quoting from the ratification declarations to disprove Wlat's ludicrous statement that "There were no illusions in 1788-90 as to the permanence of Union under law", a false statement disproven by the record, just I have shown. They created the Union with the understanding that a State could withdraw from it and reassume those powers. They said so in the very documents that created the union. Once again, some very obviously believed that it was NOT "permanent", and even said so in the documents that created the union. Wlat's statement and position is therefore completely false, as usual.
When New York agreed to ratify the Constitution it specifically stated in it's declaration "That the powers of government may be reassumed by the people, whensoever it shall become necessary to their happiness."
Virginia's declaration included these words: "the powers granted under the Constitution being derived from the People of the United States may be resumed by them whensoever the same shall be perverted to their injury or oppression"
A State's right to reassume the powers it ceded to the Union were very clearly stated when the union was created. Therefore his statement that "There were no illusions in 1788-90 as to the permanence of Union under law" is completely and totally false. You are wrong to support Wlat's obviously false statement.
BTW, secession was never ruled to be illegal before or during the war. Also, BTW, any decision declaring it illegal would be the same as declaring the original agreement void as fraudulent since some states joined with the purposely stated understanding they could withdraw and reassume those powers. Either secession was legal, or there was no union.