Chapter 2 briefly reviews some salient history concerning human migration, to place new migration challenges in some context. Brock then begins to develop the normative framework that allows us to address contemporary challenges. How can any current occupants of territory justifiably prevent anyone from migrating into their space, given our knowledge of how most settlements came into being? What case can be made that states and the boundaries they vigilantly guard are justified? Brock argues that the state can play a valuable role in delivering on justice, as one kind of permissible administrative unit, among others. For instance, delivering on our lofty justice ambitions requires attention to some quite practical details; competent administration is important for adequate planning associated with meeting needs, protecting basic liberties, along with promoting the relevant conditions necessary to sustain enduring cooperative communities. In our contemporary world, states perform important administrative functions, though various configurations could do what is required, so this is at least a partial defense of our current arrangements. The justification continues in Chapter 3.