 One question I often get is, does free immigration threaten national sovereignty? And the answer is no. America was a sovereign country from 1790 to 1875 and had, practically for all intents and purposes, open borders with the rest of the world. Now it would be odd to argue that during this time period where America fought several wars against its neighbors as well as a massive civil war that we were not a sovereign country during that time period. So historically that argument is nonsense. Furthermore, having a sovereign country does not mean that the government has to control or intimately regulate international labor markets. The power of the government to be sovereign, that is to have a monopoly on the use of legitimate force within its territory, specifically demands that it keeps out other sovereigns or other governments from doing the same or stop revolts from taking away its government power over violence in the United States. Even free flows of labor across borders do not impact that. Now of course that also means that the US government can make a restriction on the importation of Chinese infantry divisions through the immigration process, but I don't think anybody who is in favor of liberalizing immigration seriously proposes that it should also include the importation of infantry divisions of foreign countries to take over the United States. The national sovereignty argument is typically a silly argument that is employed as a last resort and very few people take it seriously.