It was our property and Lincoln was not obliged by any agreement that the Buchanan Administration made verbally (or even non-verbally if it involves the welfare of troops).
It has been adequately demonstrated that it did not involve welfare of troops.
I see you're already backing into the "it was ours and we could do as we wished" version of this argument, seeing as how the 'starving garrison at Sumter' argument made previously discharges the last few twiches of its death spiral.