At its sixty-seventh session, in 2015, the International Law Commission decided to include the topic “Jus cogens” in its programme of work, on the basis of the recommendation of the Working Group on the long-term programme of work. The Commission decided to appoint Mr. Dire D. Tladi as Special Rapporteur for the topic.

At its sixty-eighth session, in 2016, the Commission had before it the first report of the Special Rapporteur,1 which set out the Special Rapporteur’s general approach to the topic, addressed conceptual issues relating to jus cogens (peremptory norms of international law), including their nature and definition, and proposed three draft conclusions. The report also invited the Commission to comment on its preferred approach to the topic. Upon its consideration of the first report of the Special Rapporteur, the Commission referred draft conclusions 1 and 3 to the Drafting Committee. The Commission subsequently took note of the interim report of the Drafting Committee on the topic, containing the draft conclusions it had provisionally adopted, which had been transmitted to the Commission for information only.2

At its sixty-ninth session, the Commission had before it the second report of the Special Rapporteur,3 which sought to set out the criteria for the identification of peremptory norms (jus cogens), taking the 1969 Vienna Convention on the Law of Treaties as a point of departure. The Commission subsequently decided to refer draft conclusions 4 to 9, as contained in the report of the Special Rapporteur, to the Drafting Committee, and decided to change the title of the topic from “Jus cogens” to “Peremptory norms of general international law (jus cogens)”, as proposed by the Special Rapporteur. The Commission subsequently took note of the interim report of the Chair of the Drafting Committee on draft conclusions 2 [3 (2)], 4, 5, 6 and 7 provisionally adopted by the Committee, which was submitted to the Commission for information.

At its seventieth session, the Commission had before it the third report of the Special Rapporteur,which considered the consequences and legal effects of peremptory norms of general international (jus cogens). The Commission subsequently decided to refer draft conclusions 10 to 23, as contained in the report of the Special Rapporteur, to the Drafting Committee. The Commission subsequently took note of the interim reports of the Chair of the Drafting Committee on draft conclusions 8 and 9, as well as 10 to 14, provisionally adopted by the Committee, which were presented to the Commission for information.

The work of the Commission on the topic as described above has been proceeding in accordance with the successive resolutions adopted by the General Assembly under the item relating to the report of the International Law Commission.

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 cogensrules 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.

General Overviews

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 cogensbased 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 cogenshas 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.