Why? It's not enumerated. The powers not delegated ....
But still a title of nobility and therefore covered by the Constitution.
The Constitution states, 'No Title of Nobility shall be granted by the United States'. Hamilton advocated election (requirement for republican government) of the executive for life. Call him a monarch, Mr. Peanut or anything you want, you must call him something. But titles of nobility are for an 'order of men in several countries to whom privileges are granted at the expense of the rest of the people' [Bouvier Law Dictionary, Rev. 6th ed. (1856)]. Madison argued against tiles not 'because I fear the danger of any power they could confer, ... instead of encreasing they diminish the true dignity and importance of a republic, and would in particular, on this occasion, diminish the true dignity of the first magistrate himself.'
The power to approve the removal a state is delegated, as per Article IV. It specifically mentions one way, by implication any removal will need Congressional approval.
The Constitution states, 'No Title of Nobility shall be granted by the United States'.
Read Article I, Section 10, Clause 1 again.