Well both sides in the dispute acknowledged and practiced the principles of sovereignty and imminent domain. To the extent that those two principles are legitimate South Carolina was clearly acting on a basis other than just might makes right. The fort was in their territory. A libertarian might deny the legitimacy of notions like sovereignty and imminent domain, but I prefer to judge the two parties by the standards they both professed.
By what right did the US evict the British army from Detroit?
“the extent that those two principles are legitimate South Carolina was clearly acting on a basis other than just might makes right”
I suppose I should say I don’t see how South Carolina’s claims are any less a matter of Might Makes Right than the U.S.’s, then. Because similar principles dictate that nations continue to lay claim to far-flung territory no matter who happens to later claim it for themselves. We didn’t give up Guantanamo Bay after Cuba went commie, did we? Cuba, for its part, would argue that it’s their rightful land and our retaining it is a matter of Might Makes Right. But they can go suck an egg.