Property rights defined by aggression are necessary and sufficient for limiting

Property rights defined by aggression are necessary and sufficient for limiting the state, sure. But they aren’t necessary and sufficient for limiting each other in a voluntary polity.

If you want a voluntary polity in the absence of a state then you must provide a means of resolving all conflicts with each other.

We don’t have the privilege of determining what causes conflict – evolution mandated it: we can cooperate if and only if we cannot parasite or prey on each other by doing so. Otherwise evolution will punish us for it.