Jus cogens (or ius cogens) is a latin phrase that literally means “compelling law.” It designates norms from which no derogation is permitted by way of particular agreements. It stems from the idea already known in Roman law that certain legal rules cannot be contracted out, given the fundamental values they uphold. Most states and authors agree that jus cogens exists in international law. Opinions diverge however as to its exact content, sources, means of identification, and application, as well as to its precise effects and role within the international legal order. Despite persistent debates on these matters, jus cogens is now referred to in several legal instruments within and beyond the law of treaties. The 1969 and 1986 Vienna Conventions on the Law of Treaties stipulate that a treaty is void if it conflicts with jus cogens (Art. 53 and 64). The same is true for unilateral declarations, following the guiding principles adopted by the International Law Commission in 2006 (Principle 8). According to the Articles on Responsibility finalized by the same commission in 2001 and 2011, states as well as international organizations shall cooperate to bring to an end any serious breach of jus cogens, and shall not recognize as lawful a situation created by such a breach, nor render aid or assistance in maintaining such situation (Art. 41/2001 and 42/2011). Moreover, if states or international organizations are to violate jus cogens, they cannot invoke any circumstance precluding the wrongfulness of their conduct, such as necessity or force majeure (Art. 26). Finally, countermeasures shall not affect jus cogens obligations (Art. 50/2001 and 53/2011). No exhaustive list of peremptory norms has been drawn officially, but it is commonly accepted as including the prohibition of the use of force between states, the prohibition of slavery, racial discrimination, torture and genocide, as well as peoples’ right to self-determination. Given the limited number of jus cogens rules and set of effects attached to them, practice and case law are not abundant. In contrast, much scholarly attention has been paid to this controversial topic. Depending on the theoretical perspective adopted, the content and function of jus cogens can be described in very different terms. Hence there are no univocal answers to the fundamental or technical questions raised by the definition and application of jus cogens. Authors provide various solutions in this respect, the appreciation of which very much depends on whether they suit one’s very own representations of what international legal order is and how it works.
Scholarly studies relating to jus cogens can be broadly divided into three main trends, according to their theoretical premises and practical methodologies. Considering its anchorage in natural law, it comes as no surprise that jus cogens is frequently viewed as a set of superior norms sanctioning fundamental values that constrain states objectively rather than voluntarily. Its recognition in positive international law is frequently depicted as a sign of the international legal order’s moralization and maturity. Characterized by a certain idealism, Kolb 2001 presents jus cogens as a foundational structure that an emerging international community can build on and develop—formally by deepening its normative hierarchy, and substantially by proclaiming its core principles. Sharing the same idealism but expressing it in different terms, Orakhelashvili 2006 tends to explore and refine the potentialities upheld by jus cogens in order to enhance international law’s fairness and effectivity. Following a second trend, jus cogens is nothing more than what states have decided it is. Without denying its axiological character or the importance of debates as to the source of its authority, studies under this trend, including Hannikainen 1988, opt for a restrictive approach to jus cogens based on voluntarism, an approach that is sometimes presented as the only method capable of lending the concept some practicality, not to say rationality. Finally, a last group brings together authors whose shared skepticism toward jus cogens is motivated by its impractical character and ideological features. Schwarzenberger 1965 can be mentioned as a significant example of such realist approaches. The variety of perspectives on jus cogens can further be illustrated by the diverse articles assembled in Tomuschat and Thouvenin 2006. Before turning to all these elaborate analyses, any research on jus cogens should start with Frowein 2013, Carnegie Endowment for International Peace 1967, and Gomez Robledo 1981. As it is commonly accepted that jus cogens has emerged as such in international law during the 20th century, the bibliography is consequently limited, despite the undoubtable value of former studies produced, for example, by Vattel, Wolff, or Heffter.
Carnegie Endowment for International Peace. The Concept of Jus Cogens in Public International Law Papers and Proceedings. Geneva, Switzerland, 1967.
This indispensable book reproduces the papers and proceedings of the Carnegie Conference on the concept of jus cogens held at Lagonissi in 1966, and provides particularly an inspiring introductory note by Georges Abi-Saab and a well-documented and detailed report prepared by Erik Suy on the notion’s origin and limits.
Frowein, Jochen A. “Ius cogens.” In Max Planck Encyclopedia of Public International Law. Edited by Rüdiger Wolfrum. Oxford: Oxford University Press, 2013.
Frowein’s commentary on jus cogens provides a brief and concise panorama of questions related to the determination of what obligations can be considered as peremptory norms and what consequences can be attached to such qualification. The encyclopedia constitutes a useful starting point for anyone undertaking research on the subject. Available online by subscription.
Gomez Robledo, Antonio. “Le ius cogens international: Sa genèse, sa nature, ses fonctions.” Collected Courses of the Hague Academy of International Law 172 (1981): 12–217.
Gomez Robledo’s course offers an enriched analysis of jus cogens’ historical and theoretical foundations, together with a complete study of the technical questions raised by its introduction and application in international law. The course should not be missed by anyone undertaking a thorough examination of the concept.
Hannikainen, Lauri. Peremptory Norms (Jus Cogens) in International Law: Historical Development, Criteria, Present Status. Helsinki: Finnish Lawyers’, 1988.
Hannikainen’s monograph remains the most complete and in-depth analysis produced on the subject under a voluntarist approach. Its value derives from the method used to ascertain which norms can be considered as jus cogens. It is of great help to anyone confronted with concrete questions related to the notion’s application.
Kolb, Robert. Théorie du ius cogens international: essai de relecture du concept. Paris: Presses Universitaires de France, 2001.
Kolb’s monograph is useful for its thorough review of theories elaborated about jus cogens. It is also incredibly stimulating for its invitation to think of jus cogens in renewed terms as a mere legal technique designed to preserve any norm adopted in general interest (utilitas publicas) by guaranteeing its non-derogability.
Orakhelashvili, Alexander. Peremptory Norms in International Law. Oxford: Oxford University Press, 2006.
Orakhelashvili’s monograph is the most comprehensive study of jus cogens’ effects in international law, under an objective approach defining jus cogens “as a concept embodying the community interest and reinforced by its link with public morality [existing] in modern international law as a matter of necessity” (p. 577).
Schwarzenberger, Georg. “The Problem of International Public Policy.” Current Legal Problems 18 (1965): 191–214.
To Schwarzenberger, jus cogens’ recognition in international law is unrealistic and only echoes a fashionably progressive thinking. Not only is it unuseful, but it also paves the way to justifications expressing moral indignation at best and selected national interests at worst. A significant illustration of realistic approaches to jus cogens.
Tomuschat, Christian, and Jean-Marc Thouvenin, eds. The Fundamental Rules of the International Legal Order. Leiden, The Netherlands: Martinus Nijhoff, 2006.
The book gathers various contributions—both in French and in English—offering diverse points of view on specific issues raised by the definition and the interpretation of jus cogens norms, as well as the effects that such norms are capable of producing in international law.
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