[BenLurkin]

Does the US constitution give the federal government the right to retaining state land?

Not a good way to put the question, since the land was never state land.

It wasn't state land before the creation of the state, since there was no state. And it wasn't state land after creation of the state, since it never stopped being Federal land.

He needs to find another way of illustrating his point.

[Fledermaus]

It was a territory before becoming a state. Never was federal land.