This is exactly correct, but many of the Confederacy bashers refuse to take any note of this fact.
There is a lot of evidence to support secession being regarded as accepted in 1787, and very little which shows otherwise.
“Should all the states adopt it, it will be then a government established by the thirteen states of America, not through the intervention of the legislatures, but by the people at large.” — James Madison, VA state ratifying convention, June 6, 1788
“The Constitution requires an adoption in toto, and for ever.” — James Madison to Alexander Hamilton, July 20, 1788
“There is a lot of evidence to support secession being regarded as accepted in 1787, and very little which shows otherwise.”
If you have never read Charles Francis Adams Jr’s speech “Shall Cromwell Have a Statue?” you should try to find it on the internet. It’s hard to find, someone ought to reprint it, in html if nothing else.
Anyway you’ll see Adams conclude that the Confederacy had a case for secession, based upon “the old understanding” of the nature of the federal union. Lincoln chose to pretend that “the new understanding” of the federal union was the only view that existed. And nowhere was that new understanding enshrined in law. Lincoln simply imposed the new view via bayonet.
Confederacy bashers don’t like Adams’ essay at all, I suspect that is the reason it’s so hard to find. He’s inconvenient because in addition to having been a Union combat officer he’s the grandson and g-grandson of the two Massachusetts Presidents. Instead of dismissing him as a Lost Causer from Dixie they have to actually deal with his research and reasoning in the matter of secession. So they don’t.