All contracts under duress are null and void. Civil War era deals are suspect on their face, and pretending that a state constitution absolves the federal government of its prime directive is foolish. This is an issue because people with common sense recognize the wrongness of a state possessing a mere sliver of its geographic footprint.
Read the Federalist, then read the Constitution. Otherwise you will be easily confused.
Well if you follow that logic, the land belongs to either Mexico or Spain or the American Indians, depending on how far back you want to go.