In order to analyze the relationship between international, EU and national law properly, this chapter establishes a working hypothesis: a common denominator of international, EU and national law. Analogous to the historical idea of social contract theory, this common denominator is consensus. After revisiting the major criticism of consent as a (moral) obligation to obey the law, the chapter elaborates on the moral duty to adhere to the pacta sunt servanda principle. After discussing the thesis of an innate Universal Moral Grammar (UMG) that relies on an analogy to the thesis of a universal grammar of the human faculty of language in linguistics, this chapter submits that Colwyn Trevarthen’s concept of primary, secondary and tertiary intersubjectivity is more suitable for conceptualizing the origins and development of the biological setup of human morality. This chapter refers to intersubjectivity, as the decisive concept to align morality and its development with core concepts of (developmental) psychology in order to lay bare the origins of moral normativity, which is essential for us as a basis for the pacta sunt servanda principle.

The relationship between international and national law has been debated for centuries. Generally, the floor has been divided between two approaches: dualism and monism, mostly as advocated by Hans Kelsen. I argue that, in the light of major developments since their inception, such as the establishment of the European Union (EU), these theories can no longer comprehensively explain the relationship between international, EU and national law. While dualism as developed by Heinrich Triepel liberated the international legal order from an overly dominant national perspective some 125 years ago, it is not well equipped to accommodate the massive overlaps between international, EU and Member State legal orders today. In Hans Kelsen’s version, monism is an epistemological theory about what the law might be. It does not provide satisfactory guidance for the doctrinal solution of norm conflicts between international, EU and Member State law. Thus, a key focus of this book is to reconceptualize the theoretical relationship between legal orders. Even though some scholars have doubted the relevance of theoretical inquiries such as dualistic or monistic analyses of the relationship between legal orders, I cannot agree with those who trivialize this theoretical discussion by saying it would be “unreal, artificial and strictly beside the point.”1 If we continue reading Fitzmaurice’s view, it becomes clear that this is simply a dualistic argument. Yet current developments, fundamental changes and new phenomena such as the massive increase in international institutions, actors, norms and tribunals as well as adjudicators make it imperative to seek new theoretical concepts. The so-called globalization of law2 as framed in the famous constitutionalization of international law3 may be mentioned, among other developments, to elucidate the ever-growing importance of the debate on whether international, EU or national law has the final say.4

This chapter puts the developed theory to the test. First, after outlining the most important case law of the CJEU on the relationship between EU and Member State law, which has introduced primacy of EU law (also over Member State constitutional law) and the doctrine of direct effect, this chapter also displays the most important judgments by Member State constitutional courts generally holding that there are limits to the primacy of EU law. After analyzing the most important theoretical conceptions and doctrines in literature addressing the difference between the CJEU and the Constitutional Courts of some Member States, this chapter shows how consent-based monism can provide for relief. According to consent-based monism, the EU is the larger circle with regard to its Member States. All EU Member States in turn are independent smaller circles which are also part of the EU circle. The EU competence regime is decisive in this regard. It is vital to pinpoint exactly which competences have been shifted to the European level. According to consent-based monism, an “integration resistant core” must not violate any consensus that has been obtained at the level of the larger EU circle. The larger circle must not autonomously add competences without authorization by all of the smaller circles.

This chapter establishes the theory of consent-based monism. The definition of law as well as its origins start for the purpose of this book in the “legal desert.” The legal desert is to be understood as a legal vacuum, a neutral, prelegal status without any further specifications. As we are not focusing on how a just society can be conceived, the following outline will suffice: in the legal desert, a consensus between two or more individuals is widely considered to be the possibility that allows the establishment of a binding legal rule to organize social life. Consensus is thereby understood to serve as a tool for unifying individual interests and does not aim to establish any values or tools that might indicate how a just society should be organized. Choosing this basis aims at modeling the structural relationship between international, EU and national law without saying how society or the State or a supranational organization should be organized (or without arguing, for instance, whether the EU has a constitution or not). This is illustrated by figures, which graphically display the most important consequences of structurally ordering the relationship between legal orders according to consent-based monism.

This chapter critically reviews dualism, as developed by Heinrich Triepel, and monism, mainly formulated by Hans Kelsen. It argues that these theories can no longer comprehensively explain the relationship between international and EU or EU and national law and that, due to their emergence almost a century ago, these theories must be understood in their historical context. Historically, dualism was progress as the separation of international and national law helped international law become independent. Thus, dualism liberated international law from being understood as “external State law,” and was even referred to as a “cleansing thunderstorm” by the monist Alfred Verdross. The main characteristic of monism is the assumption of a single unified legal system. Kelsenian monism must face the criticism of having a highly fictitious understanding of the world: nothing less than the “unity of the legal world order” is proclaimed. To depict the most important assumptions of Kelsenian monism, this chapter looks into the Kelsenian adherence to neo-Kantian epistemology, and shows that this understanding refers to a very specific philosophical position, which has been rightly criticized by many philosophers.

The final chapter looks at the relationship between international and EU law. Also for this relationship it is decisive to, first, clearly identify how the EU can establish a consensus at the larger international level. This implies, on the one hand, that the EU is a subject of international law (Article 47 TEU and Article 335 TFEU) and, on the other hand, that the EU is competent to act concerning the subject matter (Article 3–6 TFEU). As both conditions are clearly satisfied by now, it is necessary to find out which organ is authorized to conclude an international norm (Article 216–219 TFEU). Second, it is important to determine the content of the consensus. This interpretation process is primarily the task of the level at which the consensus has been agreed. This is the international level. Third, this chapter holds that the effect of this consensus on the level of the smaller circle depends on whether the norm of the international circle is solely applicable, directly applicable or individualizing. This is demonstrated in this chapter by looking more closely at how the effect of an international treaty and customary international law unfolds within the EU legal order.

The fourth chapter offers an intermediate conclusion. Despite all of the criticism dualism and monism have faced, their persistence is remarkable. Both are still referred to in many textbooks, they are present in case law and in scholarly work. Also in practice, many (national) legal orders are still often referred to as being “dualistic” or “monistic.” Thus, there is a need to make the critical points as clear as possible in order to explain why they – as originally conceived – are of no help in answering the question posed by this book. Moreover, the preceding chapter holds that global legal pluralism cannot offer a satisfying normative account for norm conflict resolution between international, EU and national law either. Hence, prescriptive proposals to solve legal conflicts arising from different legal orders on the global plane are better not termed “pluralistic.” Rather this chapter suggests that it is more precise to refer to a necessarily common framework that addresses the question of how those conflicts should be resolved together or at least in a way acceptable to all parties.

In this book I have argued that consent-based monism provides a theoretical foundation for finding a decisive source in a norm conflict situation. It is, however, important to emphasize that I do not intend to offer an absolute and invariable solution which fits any norm conflict arising between overlapping international, EU and national legal orders. In short, consent-based monism aims to give consideration to the complex and divergent structures of international, EU and national law. Consequently, it is important not to limit the scope of the theoretical background of the relationship between international and EU or domestic law by pressing international, EU and national law into the straitjacket of a certain, predetermined legal consequence. The relationship between international, EU and national law does not follow a uniform (political) order – for example, one legal order – yet, nowadays, international, EU and national law are not completely alien to each other.1 This is in sharp contrast to old theories such as dualism and Kelsenian monism, which are considered to be incapable of coping with the major developments in international, EU and national legal orders since the inception of these grand but old theories. This important difference sets consent-based monism apart from still prevailing theories such as Kelsenian monism and dualism. While the predominant stream of global legal pluralism is also restricted when answering the question behind this book as it does not offer a satisfactory normative account, global constitutionalism suffers from major shortcomings too. Global constitutionalism presumes too many substantial values for the envisaged common normative denominator to be a helpful concept for the relationship between international, EU and national law. While global constitutionalism cannot carry the “burden of universality,” with constitutional pluralism we are likely to end up in a “constitutional stalemate.” In contrast to global legal pluralism, which was said to provide for a descriptively but not prescriptively satisfying account, consent-based monism offers a theoretical explanation of the structural relationship between international, EU and national law.