What about the ninth and tenth amendments?
Don’t they cover this area. Powers not delegated are reserved by the states. Since the states had the power to enter, the power to exit exists, and it was not explicitly delegated to the federal government. So, the power to exit the union is retained by the States.
States did not have the power to enter. They were allowed to join only if the other states agreed to let them in. So if the power to admit states was a power delegated to the United States then wouldn't the power to let them leave also be delegated to the United States as well?