Now, on page 212 I find:
"[Natural law] permits all activities that do not infringe upon the person or property of another. It takes priority over all other principles and rules that shape human society, including rules legislated by parliaments or established by contract."
Forbidding a person from simply possessing anything on his person (such as, perhaps a gun) on your property as a condition of him entering your property infringes on his person and violates Natural Law. His personal property, as long as it remains out of sight and is unused (makes no appearance outside his "bubble of personal property", does not infringe on your person or real estate in any tangible way. It may "offend" your sensibilities, but you have no right to not be offended. And any contract that attempts to negate Natural Law to suit the real estate owner's wishes is null and void since it violates Natural Law. It is exactly like the fact that slavery is not "OK, as long as you only do it on your own property".
At least, it seems clear enough to me.