What about a society that does have a state, even a limited one?
Hoppe writes:… if the government admits a person while there exists no domestic resident who wants to have this person on his property, the result is forced integration.
Now, as far as I can make out, this means that for a government to accept immigrants without someone already willing to sponsor them is anti-libertarian because it is effectively forcing everyone else to allow that migrant onto their property and forces them to support that migrant against their will.
And his solution:At all ports of entry and along its borders, the government, as trustee of its citizens, must check all newly arriving persons for an entrance ticket — a valid invitation by a domestic property owner — and everyone not in possession of such a ticket will have to be expelled at his own expense.
Furthermore:Hence, the admission implies negatively — similarly to the scenario of conditional free immigration — that the immigrant is excluded from all publicly funded welfare. Positively, it implies that the receiving party assumes legal responsibility for the actions of his invitee for the duration of his stay.
I believe that we have something of the sort already; if businesses are hiring someone from overseas to work for them in this country (and I'm pretty certain that they do this in the US too), then that business has to "sponsor" that employee in order for that migrant to be able to work, i.e. the business has to prove to the government that they have, indeed, given that migrant a job and he will be working for them for a duration of x (after which the work permit expires, although it can be reapplied for).
So, by David's argument, border control is actually more libertarian—assuming a country with its own borders and governmental system (which we have)—not less, as Doctor Vee suggests.