The idea of "owning" a piece of land yet seceding from the state is itself a totally ridiculous concept. Without the state, you "own" what you can defend. God won't come down and defend your "natural right" of property ownership. If you can defend a piece of land against the established states, then good for you. Set up whatever anarchist utopia you want in there. But if you find that a voluntarist society doesn't allow you to defend yourself from aggressive outsiders, then you have to concede the failure of the concept, because one of the most fundamental tasks of being a human, right up there with eating and breathing, is defending your tribe against other tribes. If your model of society doesn't allow you to do that, then talking about it makes about as much sense as talking about a utopia in which people don't need to eat or breathe.