ABSTRACT
To sum up the author's conclusions so far, justice requires that states open their borders or, at least, allow much more immigration than they currently do. In most cases, states should also give immigrants access to equal citizenship. This is obviously a tall order. In fact, it seems downright utopian. It’s unlikely that states will open their borders any time soon. Sovereign states have legal discretion over immigration. Under modern international law, states can both legally choose to open their borders or close them. The foundations of the modern state system are territorial integrity and sovereignty. These tenets are often thought to imply the legal right to exclude immigrants. Premodern states could not even identify most of their own citizens. Until recently, most native citizens were “undocumented”: they had no legal papers that could identify them as citizens of a state. As a consequence, it was sometimes practically impossible for governments to distinguish natives from immigrants.
