What are the libertarian positions about immigration? What our beloved Mises, Rothbard, Friedman, Ron Paul etc think about it?
And generally speaking, what's the point of taking foreigners? Why they say there is "a need" of them, even in advanced nations?
Who is "they", and from what perspective does one infer a "need"?
A libertarian justification must be in terms of private property rights, surely. Are national borders, customs & immigration procedures a manifestation of private property rights on a free market?
If the state is illegitimate, then its borders are illegitimate too. That said, most of the problems associated with the damned dirty foreignors are caused by one's own government. By making goods and people illegal, for example, it creates contraband and outlaws respectively, and the violence associated with such things.
What I ask myself is: why northern Europe countries (Sweden, Netherlands, Finland..) keep taking immigrants? No need of them there.