I understand Lew Rockwell’s anti-immigration argument as follows:
If all land and property, including roads, etc., in the US were privately owned, then it would be the case that in fact these private property owners would exclude most of the world population from coming to live anywhere in the US.
Though this is a counterfactual, Rockwell finds it plausible.
In my view, however, he is theoretically wrong, because he does not grasp the nature of roads which are by their essence publicly accessible and most likely government-owned.
I have blogged on the natural right to walk or roam the earth before: A Natural Right; Travel. By “community” I mean nothing bigger than a large business (e.g., Microsoft), university, church, or gated community, certainly smaller than a town.
Thus, public roads connect private properties with each other. They facilitate commerce and trade.
As a result, the state cannot open the roads to “natives” and close them to “foreigners,” as the natural right to walk to earth is universal. Freedom of immigration is thereby defended.
NB: This conclusion denies only the Rockwell’s specific argument against open immigration. There may be, and are, other, perhaps better, arguments against it.