International law ascribes to the conferral of a jus cogens status on a norm a particular legal significance. Bluntly put, jus cogens norms have legal consequences that norms of ordinary international law do not. International lawyers have a great many different ideas of what these legal consequences are more precisely. As of yet, the reason for this divide has not been fully clarified. This void tends to confuse jus cogens discourse on several issues such as the immunity of states and state officials in judicial proceedings originating in the violation of jus cogens norms, or the extradition of alleged perpetrators of international crimes, or again the non-applicability of amnesty laws concerning such crimes. It also impedes the justification of judicial and other legal decisions.

As this article argues, contrary to the general assumption, a lawyer’s conception of the legal consequences of jus cogens is not theory-neutral but dependent on his or her preferred understanding of the concept of law. The argument goes briefly as follows: (i) What causes international lawyers to disagree is the issue of whether or not jus cogens norms entail obligations concerned with their own enforcement; (ii) this is essentially an issue concerning the individuation of norms; (iii) depending on whether a lawyer takes the position of a legal positivist or a legal idealist, he or she uses different criteria for the individuation of jus cogens norms; and (iv) this is why, for legal idealists, jus cogens norms entail obligations concerned with their own enforcement, whereas for legal positivists they do not.

International lawyers interested in international investment law and treaty interpretation issues should consider the international award recently delivered by an ICSID Tribunal in the case of Spyridon Roussalis v Romania.1 The case arose out of the privatization of a Romanian warehouse company (SC Malimp SA). On 23 October 1998, another Romanian company (Continent SRL) entered into a share purchase agreement with the Romanian authority for state assets recovery (AVAS) to purchase 372,523 shares in SC Malimp SA, or the equivalent of a 70 per cent interest in the company. Following the acquisition of SC Malimp SA, the name of that company was changed to SC Continent Marine Enterprise SA (or ‘Continent SA’ for short).

Intertemporal law governs the applicability of international legal norms ratione temporis. According to often used terminology, intertemporal law has two different branches. This article provides clarification of the so-called ‘second branch of intertemporal law’. It does so by refuting two commonly held assumptions. First, as established in section 2 of the article, the second branch of intertemporal law is not an exception to the first branch of that law. It cannot be, since both branches of intertemporal law centre on the same legal principle: an action or a factual state of affairs must be assessed in the light of the law which is contemporary with it. Secondly, as implicated by the line of reasoning in section 2, and further confirmed by the inferential evidence cited in section 3, the practical relevance of the second branch of intertemporal law is not confined to the application of the law on the acquisition to territory. It pertains to a more widely defined group of norms in international law.

Over the last couple of years, international lawyers have hotly debated the correct way to apply Article 31, paragraph 3(c) of the 1969 Vienna Convention on the Law of Treaties. Discussions have focused on the meaning of ‘the parties’. Traditionally this expression has always been interpreted in the stricter sense of all parties to the interpreted treaty. Voices are now raised suggesting a broader interpretation. According to this view, the correct meaning of ‘the parties’ is the two or more parties to a specific dispute. Given that the two interpretations of Article 31, paragraph 3(c) will often be mutually exclusive, international legal literature provokes a review of the possible reasons that give us ground to adopt them. This article provides such a review. It arrives at the conclusion that only the stricter interpretation can be seriously defended as being correct. First, only the stricter interpretation agrees with the clear ordinary meaning of Article 31, paragraph 3(c). Secondly, even assuming that the ordinary meaning of the provision is ambiguous, a strong case can be made in favour of the stricter interpretation using other data of interpretation, such as the context, the object and purpose of the treaty, and the preparatory work.

In the practice of modern international law, if a certain understanding is advanced as the correct interpretation of a treaty provision, the proposition is assessed using the rules of interpretation laid down in the 1969 Vienna Convention on the Law of Treaties, Articles 31–33. This article is concerned with the relationship held in such an interpretation process between the preparatory work of a treaty – described as a supplementary means of interpretation in Article 32 – and the three primary means of interpretation that can be used by an interpreter citing Article 31. Judged by the wordings of Articles 31 and 32, the relationship between the primary and the supplementary means of interpretation is hierarchical. As a consequence, preparatory work may be used to determine the correct meaning of a treaty provision, only on the condition that in the earlier stages of the interpretation process, the application of Article 31 has been found to leave the meaning of the interpreted treaty ‘ambiguous or obscure’, or to lead to a result ‘which is manifestly absurd or unreasonable’. Several scholars in the area have recently argued for granting the preparatory work of a treaty a more prominent role in the interpretation process. As this article will show, such a claim builds on arguments that do not stand up to careful legal analysis. It should, therefore, be discarded as unsound.