 States are obligated to leave this state of nature among states and enter into a union of states. He considers several models of this worldwide political institution. The first is a single universal state in which the entirety of humanity is ruled directly by the single state or is subject to a single monarch. He rejects this model for failing to fulfill the function of the international institution by in effect dissolving the separateness of states rather than providing a means for peaceful relations among states. The second model is a league of states in which states voluntarily submit themselves to an organization for resolving international disputes. The league would not have coercive power to enforce its decisions, and states would be free to leave the league if they chose. He sometimes refers to this model as a “federation”, although he notes that it cannot be an indissoluble union based upon a constitution, as in the federalist structure of the United States (6:351), so it is best to refer to this model as a “league”. The third model is a state of states or a world republic of states in which each state joins a federation of states with coercive power. In this model, a state’s relation to the international federation is closely analogous to an individual person’s relation to a state. Only these second and third models receive Kant’s approval. He offers different reasons for supporting each of the two models.