Until the nineteenth century international law and domestic law were seen as two separate legal orders. The founding fathers of international law, like Emmerich de Vattel, never scrutinized the impact of international law on domestic law, because they assumed that international law, regulating inter-state relationships, did not affect the content of domestic law. This assumption was well motivated, since it reflected the features of the international law they were acquainted with, a set of rules meant to govern the behaviour of States, which did not affect the positions of individuals.

Things begin to change during the nineteenth century, when it becomes apparent that international law might affect the status of citizens, for example, in the case concerning agreements about international transports or communications. The awareness of this novel state of things prompted explicit theorizing about the relation between international and domestic law.¹ The issue was addressed by Heinrich Triepel in what it is now considered the first expression of the so-called dualist point of view. In his magnum opus, Völkerrecth und Landesrecht,² Triepel maintained that international law and domestic law constitute two separate spheres, dealing with different topics and governing different actors. In fact, the two legal orders might come into contact only when international rules affected individual or other groups within the State, and therefore within the realm of domestic law.³ It followed also that an international rule might display its effects inside the domestic legal order only after being transformed in the type of rule recognized by that legal order.

In the first half of the twentieth century, dualism became the target of several critical voices, until the work of Hans Kelsen established a novel point of view regarding the relationship between international law and domestic law, namely monism.⁴ While the monistic perspective, by itself, was not totally new—during the nineteenth century several voices claimed the supremacy of international law over domestic law—Kelsen did reformulate such a viewpoint, detaching it from naturalistic temptations and presenting it within the context of a positivist theory of international law. According to Kelsen and his followers, international law and domestic law are different branches of the same legal order: there is just one universal legal order, namely public international law, which overarches different sub-orders, the States, which complete and specify the content of international rules.

In the course of the twentieth century monism and dualism became the two poles of an endless debate. Besides the scholarly debate, the practice of national and international courts added itself as a further element of the whole picture. Under monism international law is usually regarded as immediately valid within domestic legal orders. This feature, in turn, entails that norms that can be deemed complete are self-executing, that is, capable of producing direct effects. On the contrary, dualist States consider international law and domestic law as separate spheres and require that international rules be transformed into rules recognized as valid in the domestic legal order. However, in dualist States even non-incorporated treaties may engender some effect when they are taken into account by courts interpreting domestic laws. This circumstance reinforces the suspicion that, as Jan Klabbers puts it, “the practical differences between monism and dualism may not be all that enormous”.⁵

Such a conclusion provides a compelling reason for downplaying the whole debate. The traditional divide between monistic and dualistic approaches is, in the best case, only narrow part of the entire problem. Moreover, there are strong reasons to think that the dichotomy between monism and dualism is nowadays scarcely useful to investigate international law and domestic law. Indeed, when one tries to apply this theoretical machinery to the analysis of recent case law, discomforting results follow. For example, when Jan Klabbers classifies both the European Court of Justice (ECJ) Kadi case and the United States Supreme Court Medellín case as two prominent instances of a new dualist trend within international jurisprudence,⁶ it is difficult to assuage the feeling that something in this reconstruction has gone entirely missed out.⁷ He regards the ECJ’s attempt to signal the failure of the EC Regulation implementing the United Nations sanctions against terrorism to meet the human rights requirements as an illustration of dualistic attitudes, on a par with the United States Supreme Court’s endeavour to restrict the same rights by negating the self-executing character of the International Court of Justice (ICJ)’s decisions. This produces the disquieting impression that the debate around monism and dualism has turned into a useless querelle completely detached from concrete experience.⁸

The real problem is that twenty-first century international law is quite a different thing from what it used to be when the debate between monism and dualism took off. For most of the past four hundred years, international law provided a very thin set of rules, regulating, for example, war, the conduct of diplomats, the law of the sea, or the territorial integrity of States. Since the end of World War II and particularly in the last three decades, the number of international rules has increased sharply. As a result, the international legal system is “thicker” than it has ever been before. With this scenario in sight, the classic tenets of the dualistic approach, such as those contained in some of the fundamental judgments of the discipline, like the Lotus case⁹ or the German Interests in Polish Upper Silesia case¹⁰ are no longer credible.¹¹

International law is not only thicker than before; it is also more articulated. It is more sectorial, in the sense that it harvests a plurality of thematic fields that are sometimes only weakly interrelated: human rights and humanitarian law, law of the sea, trade law, environmental law, and so on. In addition, according to some scholars, there exists a hierarchy of sources within it, which includes jus cogens, customary law, general principles of law, treaty law. The boundaries of each subset are not sharply defined, and their status within domestic law varies with the different legal orders: while some Constitutions give the highest rank to treaty provisions, others put first different sources as customary law or jus cogens.¹² Moreover, beyond the traditional sources of international law, rooted in the consent—explicit or tacit—of States,¹³ there is a new array of rules, regulations, standards, recommendations originating from international organizations, NGOs, multinational companies, and not easily linkable to the consent of States. This set of norms, known as “global law”, is now the centre-stage of the theoretical debate,¹⁴ because it raises formidable challenges to every attempt to define a proper criterion for distinguishing between law and non-law, and therefore for drawing a comprehensive map of valid law.

It is also worth noticing that within this landscape the role of courts, both international and domestic ones, acquires a new prominence. This fact may be viewed as a consequence of the growing complexity of international law, since such complexity precludes the formation of stable agreements and assigns to courts the creative task of reconstructing the hierarchy of normative sources. Such a predicament leads eventually to increasing the practical relevance of principles as an indispensable tool in the process of outlining the structure of valid law. In fact, while international treaties—such as European treaty law—resort widely to general principles in order to assure the dynamic character of their provisions without dismissing their universality,¹⁵ these principles are not strictly formal like general principles of law but possess frequently substantive import.¹⁶ Moreover, they are generally to be insulated and detailed by courts in their attempts to find the correct solution to the cases submitted to them. This state of affairs provides the reasons for searching out another interpretive key to the relationship between international law and domestic law, which does have the property of being more centred on the concrete practice of courts. It is my claim that a sounder analysis of this relationship should be based on the central notion of recognition.

As I argued above the debate between monism and dualism seems to have come to a dead end. The main problem is that this dichotomy reflects a static conception of international law, according to which international law and domestic law operate as a single—or, rather, a couple of—fixed set(s) that do(es) not undergo any substantial variation over time. On the contrary, the prevailing image of global law is one of rapid flux, where a more stable core of acts, easily identifiable as law, is surrounded by a nebula of rules, standards, etc. whose exact qualification is somewhat uncertain. Against this background an approach that centres on the processes through which new rules and regulations can gain the status of law is definitely more fruitful than one which gets lost in endless distinctions about the relationships between the international system and national legal orders.

In order to pursue this kind of inquiry it is worth building on the concept of recognition. Reference to recognition of law inevitably evokes the name of H.L.A. Hart. As it is widely known Hart thought that every legal system necessarily contains a rule setting out the criteria of legal validity, that is, a (secondary) rule which determines which rules are binding.¹⁷ However, Hart did not think that international law could display rules of recognition comparable to those pertaining to national legal orders.¹⁸ Be this as it may, in what follows I will try to explore a different notion of recognition that may prove useful, that is to say, the Hegelian one.

The concept of recognition is widely employed by contemporary philosophers. Yet, to avoid a long inquiry into its remote origins, it is fair to say that its probably most fertile elaboration can be found in Hegel’s Phenomenology of Spirit.¹⁹ Hegel introduces the concept of recognition in the fourth chapter of the Phenomenology, as a key element in the transition from consciousness to self-consciousness. After considering the first way in which self-conscious subjects conceive themselves, as pure will or desire that affirms itself in overcoming the world around it—which turns out to be unsatisfying, since the subject continuously needs new objects to overcome—, Hegel moves to the idea that self-conscious subjects require the recognition on the part of other self-conscious subjects: “Self-consciousness exists for and in itself when, and by the fact that, it so exists for another; that is, it exists only as something acknowledged”.²⁰