A quibble: the Constitution says nothing about states not being able to exit. In fact, the 9th and 10th amendments say that powers not delegated to the Fed are

A quibble: the Constitution says nothing about states not being able to exit. In fact, the 9th and 10th amendments say that powers not delegated to the Fed are reserved for the people and states...strongly suggesting that states _DO_ have a right of exit. So let's not say "the right of states to BREAK their contract" and instead say "the right of states to EXIT their contract".