A common argument against returning to the immigration policy of 1790-1875, where virtually anybody in the world could immigrate to the United States, is that such a policy would diminish America’s national sovereignty. By not exercising “control” over borders through actively blocking immigrants, as the argument goes, the United States government would surrender a supposedly vital component of its national sovereignty. But that argument is mistaken as there is no inherent conflict between free immigration and national sovereignty.
The standard Weberian definition of a government is an institution that has a monopoly (or near monopoly) on the legitimate use of violence within a certain geographical area. The way it achieves this monopoly is by keeping out other competing sovereigns (aka nations) that would be that monopoly of legitimate coercion. The two main ways our government does that is by keeping the militaries of other nations out of the United States and by stopping insurgents or potential insurgents from seizing power through violence and supplanting the U.S. government.
U.S. immigration laws are not primarily designed or intended to keep out foreign armies, spies, or insurgents. The main effect of our immigration laws is to keep out willing foreign workers from selling their labor to willing American purchasers. Such economic controls do not aid in the maintenance of national sovereignty and relaxing or removing them would not infringe upon the government's national sovereignty any more than a policy of unilateral free trade would. If the United States would return to its 1790-1875 immigration policy, foreign militaries crossing U.S. borders would be countered by the U.S. military. Allowing the free flow of non-violent and healthy foreign nationals does nothing to diminish the U.S. government’s legitimate monopoly of force.
Many of those who complain that free immigration would reduce U.S. national sovereignty really mean that the U.S. government will have less power. That is absolutely correct. If free immigration was the law of the land then the government would not be able to arbitrarily stop immigrants for any virtually any reason, the power of American bureaucrats to capriciously exclude immigrants and punish American businesses who want to hire them would be diminished, the outcomes of attempting to immigrate would be ex ante more predictable for the immigrant, and the U.S. government’s power in relation to immigration would be brought in line with our common law traditions. Those benefits to free immigration are, by the way, also the benefits of limited constitutional government in every other sphere of human activity.
Complaining that free immigration would limit government power and therefore limit national sovereignty is akin to complaining that the Constitution limits government power and therefore limits government sovereignty. Such a limitation of government power is the point of such restrictions. Only by limiting the power of our government over our lives can we maintain some degree of individual liberty. In so far as the Constitution or free immigration would limit government power then they are checks on government action. But those checks on government actions do not diminish the national sovereignty of the U.S. government and do not allow foreign sovereigns or governments to gain power over us at the expense of our government’s abandonment of it.
There is a contradiction between constitutionally limited government and near limitless immigration controls but there is no such contradiction between U.S. national sovereignty and free immigration. The exceptions to this is the movement of people into the United States that would seek to destroy U.S. national sovereignty like foreign military forces (who are rightly called “invaders”), insurgents, spies, terrorists, or other limited and identifiable non-immigrants. Blocking the vast majority of all such people from entering is actually made easier by freer immigration for two reasons. First, the government could more easily identify and exclude them through limited and targeted border controls that are currently difficult because most border controls target economic immigrants rather than legitimate security concerns. Second, if any peaceful and healthy person could come to the United States lawfully then anybody attempting to enter unlawfully would raise red flags – allowing the government to focus scarce law enforcement resources on people most likely to be security threats. In that way, our current restrictionist border controls likely impede the government's power to exclude threats to its sovereignty.
There is a historical argument that free immigration and U.S. national sovereignty are not in conflict. From 1790-1875 the federal government placed almost no restrictions on immigration. At the time, states imposed restrictions on the immigration of free blacks and likely indigents through outright bars, taxes, passenger regulations, and bonds. Many of those restrictions weren’t enforced by state governments and were lifted in the 1840s after Supreme Court decisions limited the power of state governments to regulate international commerce. During that time, the United States fought two wars against foreign powers – the War of 1812 and the Mexican American War – and the Civil War, which was the largest war in our history. The U.S. government’s monopoly on the legitimate use of force during that time was certainly challenged from within and without but the U.S. government maintained its national sovereignty even with near open borders. The U.S. government was also clearly sovereign during that period of history. Those who claim the U.S. government would lose its national sovereignty under a regime of free immigration have yet to reconcile that with America’s past and the arguments above. We do not have to choose between free immigration and continued U.S. national sovereignty - we can have both just as our ancestors did.