Gary Becker: "Open immigration to America worked well during the 19th century because the government did very little for immigrants and their families. How immigrants voted after becoming citizens also mattered little because government decisions were not so important. With the growth of government during the past half century, neither of these conditions continues to hold, so the case for open immigration is fatally weakened." Hat tip: Mike Rappaport at the Right Coast. I would throw in the fact that the American establishment has a much weaker commitment to assimilation these days, that modern communcations allow immigrants to retain much stronger ties to their homelands, and that the courts require the government to allow dual citizenship. Also, if we're serious about preventing terrorist attacks in the U.S., wouldn't it make sense to ban immigration from the countries where terrorists are most likely to come from (e.g., Saudi Arabaia, home of 15 of the 19 9/11 hijackers?) Though not a panacea, it a lot cheaper both in terms of monetary costs and civil liberties than additional dubious homeland security initiatives. I'm generally pro-immigration and pro-immigrant, but I think there needs to be an intelligent, informed debate on American immigration policy, with the goal of replacing the haphazard mess we have now.