"If the limits of immigration are bounded by political psychology rather than by economic necessity, a series of uncomfortable questions arise."

"What moral weight, for instance, should be accorded to the human desire for cultural continuity? Taken to an extreme, it could legitimatize the sort of ethnic separation that white nationalists aspire to when they recite their credo known as the Fourteen Words: 'We must secure the existence of our people and a future for white children.'.... On the other hand, there’s the question of whether rich countries have Good Samaritan responsibilities to help poorer ones.... Modern political philosophers have largely found extreme limitations on people’s ability to migrate to be unjustifiable.... If humans all have equal moral worth, how can it be fair to let the dumb luck of birth determine opportunity to such an extreme degree?"

Writes Idrees Kahloon in "Economists Love Immigration. Why Do So Many Americans Hate It? In a democracy, a policy appraisal has to contend with political as well as economic consequences" (The New Yorker).

It’s notable that neither John Rawls nor Robert Nozick, the past century’s two greatest thinkers about the social contract, was eager to reckon with the matter of migration in his magnum opus. In "A Theory of Justice," Rawls argued that the rules ordering a just society are the ones we would agree to behind a veil of ignorance about our position in it. If the entire world could be placed behind one such veil, would it settle for the present-day system of tightly regulated borders? It seems unlikely, but Rawls dodged the issue by limiting his analysis to 'closed' societies, in which migration was assumed away....

In “Immigration and Democracy” (Oxford), Sarah Song, a professor of law and political science at Berkeley.... writes, “part of what it means for a political community to be self-determining is that it controls whom to admit as new members.”... 

But America today has forty-five million foreign-born residents—the most of any country, and as many as the next four combined. And Biden, loudly hawkish on unauthorized immigration, has quietly expanded the number of legal admissions.... If America’s [demographic transition] proceeds peacefully, it would mark success for one of the greatest experiments any democracy has ever tried, and help secure economic primacy over closed and sclerotic societies like China’s....