Tom, (re my previous post)– yes, and, besides the prominent libertarians in the JLS symposium issue, and the ones you cite–Milton Friedman, Gary Becker, and Thomas Sowell–there’s also Stephen Cox, editor of Liberty; and, of course, Mises, who also rejected the idea of completely unrestricted immigration (Omnipotent Government, p. 105):

“These considerations are not a plea for opening America and the British Dominions to German, Italian, and Japanese immigrants. Under present conditions America and Australia would simply commit suicide by admitting Nazis, Fascists, and Japanese. They could as well directly surrender to the Führer and to the Mikado. Immigrants from the totalitarian countries are today the vanguard of their armies, a fifth column whose invasion would render all measures of defense useless. America and Australia can preserve their freedom, their civilizations, and their economic institutions only by rigidly barring access to the subjects of the dictators. But these conditions are the outcome of etatism. In the liberal past the immigrants came not as pacemakers of conquest but as loyal citizens of their new country.”

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