Buying land is still using state coercion (in a mild and accepted way) to deprive everyone else of it, it's a natural resource.
The strength of a government, and thus, the property rights it “grants” people, is the degree to which it has been successful in establishing a violence monopoly.
People in countries like Finland have a 'freedom to roam', showing that property rights don't need to include the right to control who can enter a piece of land.
This dates from a time when people recognized property ownership, but there was no government monopoly on violence. (See especially the Icelandic Commonwealth and the Icelandic sagas.)