We published an article on how the Scholastics approached the issue of immigration; it was primarily historical, leaving modern application up to the reader. For my part, I have a quick note of dissent: one of the things I just cannot come to terms with about the open borders position is the claim that there is a "right to travel" other places. Quoting Vitoria, we read:
Second, in the beginning of the world, when all things were held in common, everyone was allowed to visit and travel through any land he wished. This right was clearly not taken away by the division of property; it was never the intention of nations to prevent men’s free mutual intercourse with one another by this division. . . .
This is so obviously false on libertarian terms its hard to imagine agreeing with it at all from a libertarian lens. It is precisely the establishment of private property that prevents people from having the right to travel on any lands they wish. Indeed, the only lands that can be travelled on are those that are either unowned or whose owner granted permission. Men don't have the right to travel on lands they do not own. The only "right" someone has is to use his own property as he sees fit or to homestead currently unowned resources.
All this of course does not take away from that article's main point, which is that "open borders is the civilizational norm, and that only serious crimes justify prohibiting migrants from travelling to, or residing in, a particular nation." Historically, even as someone who is not an advocate of open borders, I have no problem with this being this historical way of things. In my own view, whether a border is relatively open or closed will depend on the social setting and the homogeneity of various cultural habits and norms.
One can imagine living in a world where there is a moral presumption of the harmlessness of immigration. But I do not think our world is theirs. Old Europe was so much different than the modern world, and immigration mixed with multicultural social democracy is largely a driving force of upheaval and social degradation.
I agree with the Hoppe-Rockwell-Rothbard stance here: mandated open borders are an assault on private property and a means by which international governments have increased their power and undermined the way of life of so many in Europe.
The debate between an "open" border and a "closed" border is indeed a moot debate. Borders, like property lines, depend on context, permissions, intent, prudence, etc. The very existence of a border implies these things, and the protectionist-nationalistic strain of pro-border wall and so forth are likewise wrong in their own authoritarian approach.
The true solution in our time is to let localities control their own borders.