Nonsense. Federal property? There was no more federation that included South Carolina. You sound like an aggressive northerner. You sure do love the concept of that all powerful federal government.
Simply declaring themselves unilaterally disassociated from the union didn’t free them from their obligations or give them carte blanche to steal whatever they felt like stealing.
Unless or until legally resolved to mutual satisfaction the fort and the ground it say on belonged to the United States.
Lamer insults notwithstanding.