Many who favor libertarian politics but oppose open immigration use the existence of a welfare system as a reason to not favor open immigration. Setting aside the reality that most non-natives are not eligible for most welfare benefits, the argument has emotional appeal. It seems unfair to give non-citizens benefits that citizens pay for through tax dollars and that may raise citizens' taxes. If you abolish the welfare state, these opponents say, they would favor open immigration. But even this acknowledges that open immigration is the default libertarian position, since their argument is to overcome the default with a justifiable restriction on human liberty.
Their position ignores that a restrictive border necessitates highway checkpoints, an immigration police state, warrantless searches of property, forcible separation of children and their parents, and a host of other egregious practices.
The reality is that most immigrants do not come to take advantage of the welfare state, nor is the federal government required to provide aid to foreigners. In fact, some economists have calculated that open immigration actually reduces the burden of the welfare state.
While this argument has some initial emotional appeal (and because Milton Friedman said it), this appears to be yet another ad hoc reason to oppose the free movement of people and deny them their right to flourish.
This question is from Faith Seeking Freedom: Updated & Expanded, available in paperback, PDF, and Kindle.