Analogies are always so troublesome because they are always so inexact. If my motorcycle was in your hotel room and you decided to take ownership of the room - including my motorcycle - do I have an obligation to surrender it? The answer would be no, unless you present a clear and present danger to my safety.
Sumter was built on ground ceded IN PERPETUITY to the federal government. The structure itself was paid for by federal monies. It did not belong to South Carolina. Even though it stood within the boundaries of the state it wasn’t state property before the insurrection and it wasn’t cornfederate property after the insurrection. Because it was seized as an act of war it was considered booty until the federal government reclaimed it.
Perhaps we should rightly call it the War of Southron Aggression.
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.
Note that the North had no more rightful claim to federal property than the South did. When you get divorced joint ownership ceases and property is divided. One spouse does not get to claim everything, just because it was once mutually owned.
Also note that the South didn’t attempt to garrison Northern forts or claim areas outside of the Confederacy.