Why do migrants enjoy some of the rights associated with citizenship? Existing accounts typically answer this question in terms of obligation—of a duty on the part of states to confer citizenship. Moreover, scholars tend to lump together the rights conventionally associated with citizenship when they answer this question. In contrast, this Article disaggregates the rights associated with citizenship, asks what both states and migrants want, and inquires into how the suite of rights associated with citizenship might advance those interests. States want to encourage migrants to enter their territory and to make country-specific investments, but states also have an interest in being able to remove migrants or make their lives less comfortable if circumstances change. However, migrants will not enter and make country-specific investments if the state can easily remove them or change the conditions in which they live. Accordingly, the optimal “migration contract” between the state and the migrant reflects the trade-offs between commitment and flexibility. We discuss ways in which basic rights to liberty and property, political rights including voting, and other rights may embody the optimal contract in different circumstances.