There is a way in which great thinkers remain contemporary. This, I believe, is in virtue of the possibility of a continuous re-actualization of their thought in view of contemporary challenges. It is in this sense that I consider Kant’s cosmopolitan theory as guiding our understanding of the standards of the legitimacy of international law. For Kant law is legitimate if it reflects an ideal of moral freedom. Following from this premise, public right generates a “rightful condition” — a constitution (constitutio) — at both the state and at the international level. This latter notion is constructed on the model of the categorical imperative and particularly on the idea of a submission of one’s maxims as if one were “a law-making member in the universal kingdom of ends” (Kant, Grounding for the Metaphysics of Morals , 4:434). For Kant public right does not only enhance freedom within the state, that is internally in the form of domestic right (civil constitutional law), but also externally through international right — jus gentium. Kant’s innovation, however, is the following: He thinks that international law should be supplemented by yet a further law component that regulates the relations between states and non-citizens through the cosmopolitan right as a right to hospitality (Kant, Perpetual Peace  8:358).
Now, if this is helpful to sketch the normative design of Kant’s legal cosmopolitanism, then, with regard to the constitutional implementation, the question becomes how to realize the progression towards such a global legal condition. Precisely on this point interpreters have been challenged and puzzled by Kant’s apparently contradictory solutions. My interpretation, instead, holds that Kant held only one single, coherent view all the way through his writings, a view that he illustrated in different ways by keeping faith to the idea of a gradual process of institutionalization of cosmopolitan law. Kant had a plurality of transnational arrangements in mind, which have too often been overlooked by scholars or that were merely considered as a sign of theoretical unclarity. For example, what Kant calls Völkerstaat, which I translate as “the multistate confederation”, presents features that differentiate it from both “the league of states” or “the federation”, for which he uses the words Völkerbund or Föderation, as well as from the congress of states, which he calls Kongreß (Kant, Doctrine of Right, , 6:350-351). The Völkerstaat refers to the same political entity as “the world republic” (Weltrepublik) but each term emphasizes, respectively, the internal pluralism and the “stateness” component or, alternatively, the (republican) form of government and the unity of the state components (Kant, Perpetual Peace , [8:357]). In turn the world republic differs from the “world monarchy” whereby the latter is categorically excluded by Kant as a feasible option for the international order (Kant, Perpetual Peace , [8:367]).
These terminological distinctions help to interpret one of the most crucial as well as puzzling passages of Kant’s cosmopolitan theory: the famous paragraph of the Perpetual Peace where Kant draws the distinction between what is right in theory (in thesi) ― as with the institutionalization of a world republic ― and what is right in practice (in hypothesi), as with the federation of states as a negative surrogate (Kant, Perpetual Peace  8:35). But it is exactly where interpreters have dismissed Kant’s important introduction of a third terminological distinction: the Völkerstaat. What was Kant’s reason for this? The reason, I believe, is that Kant thinks that the world republic as an ideal cannot be achieved, and even if it were, it would soon turn into a despotic state (Kant, Perpetual Peace , 8:367). We have to start from the most realistic and nearest configuration. The league of states, though suboptimal, serves this purpose even though it does not represent a desirable end. But it can serve as a starting point. The question then is towards which model should we proceed? This is where the notion of the Völkerstaat as the “multistate confederation” (as I translate it), and its regulative ideal for the transitional progression towards peace comes into play. The multistate confederation represents an “as if” standard for the coordination of states according to a lawful condition. In this way Kant formulates a standard for the formal unity of international law despite the absence of an ultimate adjudicative authority that we would find in a world republic. Such unity is characterized by a certain degree of internal pluralism (it is a multistate confederation after all) which is shaped in accordance to the standards of cosmopolitan right. These standards approximate what we call human rights standards or the principle of non-refoulement, to draw a parallel with the contemporary legal arrangements.
Let me conclude with one further remark for a re-actualization of Kant’s cosmopolitan insight. Kant’s formal concept for the unity of international law helps us to further our understanding of the standards of validity of international adjudication today. If one considers some of the most prominent cases illustrating, for instance, the controversy between the European Court of Justice and the United Nations Security Council Resolution 1267, like the Kadi case, it becomes apparent, how the interpretation of a formal standard of unity helps orient transnational adjudication. The condition of the formal unity of international law sets a universalizable standard of judicial reasoning as it establishes that any valid adjudication at the international level has to be valid “as if” it were to be applicable in the context of one single multistate confederation (Völkerstaat). The contemporary proliferation of horizontal and vertical networks and regimes as well as the so called “judicialization” of international relations represent just one further step in the direction of what Kant already saw as a new standard of validity for international law in view of individual claims of cosmopolitan citizenship.
Claudio Corradetti’s article “Kant’s Legacy and the Idea of Transitional Jus Cosmopoliticum” is forthcoming with Ratio Juris 29, no. 1 (2016). Access is already available through the author’s SSRN page.