Any of them, in the same way they've ordered the shut down bases many, many times in the past.
This comment is sorta like moving the goal posts. Shutting down a base is not the same as ordering a withdraw and giving up the real estate.
Lincoln could have withdrawn and given up the land at his own whim. It would have had no significant impact on the Union's ability to defend itself.
Evacuating Pearl Harbor and giving up the land would have been not only horrifically costly, it would have been seriously detrimental to US defense.
You have to remember that the normal condition of Fort Sumter was empty. Nobody was stationed there by actual orders until after the Civil War, and they only did that to make a symbolic point. Eventually those troops were withdrawn, and it has stood empty of a garrison ever since.