The Heartless Libertarian rants about immigration...

... but he's not ranting about it in a Libertarian fashion. Actually, he's complaining that he doesn't subscribe to the open-borders position. And he's got a point; the official libertarian position on immigrants and border control only makes sense if the rest of the libertarian platform gets enacts, or something fairly close to it. So, with that in mind, let me explain how it is supposed to work:

First, under a libertarian government, the government would not be responsible for providing things like welfare or health care to those who can't afford them. Under the current system an illegal immigrant has access to all sorts of government benefits without any obligation to pay the taxes that supposedly fund those benefits; if you remove those benefits you remove one of the things that makes illegal immigrants an economic drain on the country.

Second, under a libertarian government, taxes on personal income would be much lower, or even eliminated completely. This effectively removes the economic conditions that make employing an illegal immigrant so much cheaper than employing an American citizen. Restore parity in the cost of labor, and you're back to a free market again.

Third, under a libertarian government, many of the enforcement difficulties for immigration law are reduced. It's easy to get into the country, so smuggling people in becomes much less of a problem; the only people being smuggled in are people who would be denied legal entry, and those people would only be the ones we really want to stop -- that is, terrorists. So anyone getting smuggled across a border becomes fair game for severe enforcement efforts.

Fourth, under a libertarian government, the people are generally responsible for their own defense. (This is also true under the present government, of course, but in a libertarian government they would be told this and expected to arm themselves accordingly). This reduces the crime problem posed by illegal immigrants, since they are among an armed people expecting to defend themselves. Since many illegal immigrants are also legalized, there's much less of an incentive to commit crimes. The combination should be very effective.

Finally, in times of war, no one seriously expects even a libertarian government to maintain a completely open border policy.

Overall, he's right -- a libertarian immigration policy doesn't make sense with our current government and legal system. But it makes perfect sense once you replace our current policies with libertarian policies.