“It is in the linkage between freedom of movement and equality of opportunity that the analogy with feudalism cuts most deeply. Under feudalism, there was no commitment to equal opportunity. The social circumstances of one’s birth largely determined one’s opportunities, and restrictions on freedom of movement were an essential element in maintaining the limitations on the opportunities of those with talent and motivation but the wrong class background. (Of course, gender was another pervasive constraint.) In the modern world, we have created a social order in which there is a commitment to equality of opportunity for people within democratic states (at least to some extent), but no pretense of, or even aspiration to, equality of opportunity for people across states. Because of the state’s discretionary control over immigration, the opportunities for people in one state are simply closed to those from another (for the most part).”