It is my understanding that a state could leave, as a final measure to protect itself against a tyrannical Federal government, because there are sometimes no other options and the Union was not meant to be a backdoor way to enslaving smaller states in favour of the large states.
However, although a state could option for secession along with whatever conditions they agree to upon leaving, the feds don’t have to let back in so freely. The feds can impose all the conditions it wants to admitting a state, but it can’t keep a state that wants out.
Before 1869, that was my understanding of the arrangement to joining the Union.
He wrote about the Declaration of Independence being a compact between the states (and as Jefferson put it, a "mutual pledge"). As I've written during the Article V Convention of States threads, there is a difference between "throwing off" a tyrannical government and seceding from the union altogether. One can change the government without leaving the nation. The former was the intent, not the latter.
The "backdoor enslaving of smaller states" is more a function of a runaway federal government that has been allowed to govern beyond its enumerated powers. I blame the 17th amendment for this, which is why the solution is for the states to call an Article V convention to propose structural changes to take back what Congress will not willingly give back.
The problems that all states face (and not just the small states), is that the federal government no longer respects the states as the controlling entities they once were; the party blocs are now the controlling force in the United States and all the states are their subjects. It was supposed to be the other way around.
The solution is not to take their marbles and leave. No state can survive as its own independent nation. If one state tries this, I believe it will balkanize the entire continent and we will become like Europe.
-PJ