My eye caught this article, which stands in a long tradition among libertarians.
It is the kind of fairy tale theory that gives liberal thought a bad name in general, and classical liberal thought in particular, as it is often confused with libertarianism in the US.
My problem with arguments like these is that they make logical sense, but are practically non-sensical at the same time. I am more than willing to admit that in the ideal libertarian world free immigration indeed is a right. Yet I do not think arguments like these help us to get that libertarian ideal one inch closer. On the contrary, I am afraid it only fosters disdain and outright disbelief, even among potential supporters.
The main problem of course is that there is no ideal libertarian world. Yet libertarians all too often do not seem to care about that. They rather continue to argue about what fairy tales makes the most logical sense, rather than using their sometimes brilliant minds to come up with ideas and theories to actually foster a more liberal world. Let alone a classical liberal or a libertarian world.
To make a case for free immigration on the basis of rights is to deny the property rights of current populations. Roughly, that argument goes like this: in this world most immigrants will make some claim to these existing property rights once they arrive in their host country. Higher taxation to pay for the immigration system is one thing, but also think of housing, claims to health and medical systems, social welfare programs, schools, roads, et cetera. The majority of the current population has put money into (these) public goods, certainly in Europe, and thus property rights were created. These should be protected and can only consensually be changed.
Also, there are more intangible effects, think for example of the change in culture and social cohesion, certainly before the new arrivals are fully integrated. Hayek warned against precisely these destabilizing effects of large groups of immigrants entering a relatively homogenous territory, drawing on his own Viennese experience in the interwar years. He openly supported Margaret Thatcher to this end in a letter to The Times on February 11, 1978, which were followed by further explanations in the same newspaper in the weeks thereafter.
This is not to say we should all build (or rather attempt to build) walls, or close off borders completely. Some form of immigration is indeed called for, if only out of humanitarian perspective. That is something completely different than free immigration though.