Yeah, I’ve always thought it was pretty obvious that the framers felt secession was perfectly fine. The fact that they didn’t mention it in the Constitution is pretty weird, and probably means one of three things:
(a) it was so obviously unconstitutional it didn’t even bear mentioning;
(b) it was so obviously constitutional it didn’t even bear mentioning;
© they didn’t feel like creating strife by opening a Great Debate ™ on the subject, so they just kinda forgot about it.
© doesn’t seem very likely, since they dealt with a lot of super-contentious issues head-on, e.g. slavery, export and import taxes, etc. Why deal in detail with the issue of how states can be added to the union and forget about how states could leave.
(A) doesn’t seem very likely, since state’s rights are rarely enumerated in the Constitution; usually, only limitations on state’s rights are enumerated (no duties on imports from other states, no maintaining “troops of war”, etc.) So if secession is one of the few things a state can’t do, it is very odd for the founders to be silent about it.
That’s why I stick with (b). It stands to reason that if the framers had fought on died for the rights of nationhood, they would be reluctant to deny those rights to the people they had fought alongside. If there is a power to create a political union, there must logically be a power to dissolve one, as the framers had proven by driving the British out. And the 10th Amendment specifies exactly who holds all the powers not otherwize provided for.
Any similarity in the above text to an English word or phrase is purely coincidental.