[Non-Sequitur]

The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.

The Constitution delegates the power to approve the admission of states to the Union, and any change in their status while part of the Union. Clearly leaving the Union is included in this.

[4CJ]

The Constitution delegates the power to approve the admission of states to the Union, and any change in their status while part of the Union. Clearly leaving the Union is included in this.

Please stop making this up. The Constitution allows Congress to regulate the process of admission of new states, the creation of a new state from parts of an existing one. It is absolutely silent about one leaving, seeking approval to leave, or in any way preventing one from leaving.