Professor Momtaz begins his courses by examining the question of the evolution of international law from the equality and homogeneity of rules to the superiority of one (jus cogens) over another (ordinary rule) and the competent authority to decide on this matter. Professor Momtaz addresses the extension of the phenomenon of imperativité from contract law to other sources of international law. On the question of the identification of jus cogens, he does not consider the non-violability of norms as a criterion for becoming jus cogens, but correctly introduces the nature of the rule as the most important criterion. When it comes to the competent authority who could decide on the peremptory nature of the rule, Momtaz considers the recognition and acceptance of jus cogens by states to be the decisive factor. However, it seems that international judicial bodies in particular the ICJ have played the most important role.

Momtaz recalls the effect of a conflict between a treaty provision and a peremptory norm, which leads to the nullity of the former, but does not go beyond it. The shortcoming of this section is that it does not address the compatibility of other international obligations and sources with jus cogens. The author then analyses the conformity of certain controversial acts of States and international bodies with jus cogens and concludes that the protection contained in Article 53 of the VCLT that "a treaty is void if, at the time of its conclusion, it conflicts with a peremptory norm of general international law", should be extended to the unilateral acts of States. That being said, when he discusses the compatibility of Security Council resolutions with jus cogens and the competent authority to deal with it, Momtaz remains very cautious. Although he concludes that a resolution contrary to the rules of jus cogens is subject to a fate similar to that provided for treaties in Article 53 of the VCLT, namely the nullity of the resolution, but on the review of the compliance of Security Council resolutions with jus cogens by international or regional courts, Momtaz approves only the indirect control or review of these resolutions by domestic and regional courts, such as the European Court of Justice, not the international judicial bodies like the ICJ.

On the confrontation between jus cogens and ordinary rules of international law, Professor Momtaz addresses the consequences of a breach of a peremptory norm of international law. He explains that the famous dictum of the ICJ in the Barcelona Traction case, according to which the obligations deriving from the peremptory norms are of erga omnes nature for States, paved the way for the contamination of the law of State responsibility with the hierarchy of rules. He first deals with the dual regime of international responsibility based on the importance of the breached obligation and the legal interest of non-injured States to invoke the responsibility of the offending State when the breached obligation is of an erga omnes nature. However, his conservative position on certain issues, including universal jurisdiction, is not beyond reproach. In fact, concerning the jurisdiction of the domestic and international courts to prosecute the perpetrators of the violation of peremptory norms, noting the judgment of the ICJ in the Arrest Warrant case and the resolution of Institut de Droit International (IDI) on the "universal jurisdiction", Momtaz argues against the extension of universal jurisdiction to prosecute the perpetrators of international crimes, calling it an "arbitrary exercise of universal jurisdiction". He agrees with the prevailing doctrine and findings of the IDI that such jurisdiction is not applicable unless the accused is present on the territory of the country seeking to exercise such jurisdiction.

Momtaz seems to take a cautious approach with regards the international community's response to violations of the obligations aimed at protecting its interests and values. He is skeptical and pessimistic about mechanisms and reactive measures, including universal jurisdiction and humanitarian intervention. Pessimism about universal jurisdiction is justified. Like any other mechanism - including the UN Security Council, the Human Rights Council, etc. - universal jurisdiction can be, and is, used selectively and irresponsibly. However, this argument does not seem to be a sufficient reason to set aside the legal mechanism of universal jurisdiction. In international relations, bad law is better than no law. A politically motivated or even selective and arbitrary application of universal jurisdiction is better than the absolute immunity of international criminals from trial and prosecution.

Finally, Momtaz raises important and interesting questions - the same question that was raised in the Jurisdictional Immunity of States (Germany v. Italy) case before the ICJ – whether, in case of conflict between "jus cogens" and "immunity of States", the latter loses its effect. After reviewing some domestic rules that make such an exception to the general rule of immunity (including U.S. and Canadian law), Momtaz recalls and agrees with the above-mentioned judgment in which the ICJ concludes that under customary international law as it presently stands, a State is not deprived of immunity by reason of the fact that it is accused of serious violations of international human rights law or the international law of armed conflict.