d. Where such persons are subject to criminal proceedings before certain international criminal courts, where they have jurisdiction.235 Of most practical importance is the exception listed in (c), as the chances of (a) and (b) happening must be considered very limited, and the scope of (d) is as yet extremely limited. III. THEMATIC SUMMARY OF SOME CENTRAL ISSUES PERTAINING TO THE CONVENTION 2. IMMUNITY TO HEADS OF STATES AND DIPLOMATS? 3. THE PROHIBITION OF TORTURE AS A NORM OF JUS COGENS As upheld by the Court, certain incumbent representatives of States, including diplomatic agents, enjoy complete immunity (so-called immunity rationae personae) in conventional and customary international law, based on a notion that such immunities are necessary to ensure the efficient performance of their functions on behalf of their respective States.236 According to (c), the same group of State representatives, after leaving office, enjoys functional immunity for all acts performed in the exercise of an official capacity (so-called immunity rationae materiae). It is thus not the nature of the acts which determines whether or not jurisdictional immunity applies to former State representatives, but whether or not the acts in question were performed in an official or private capacity. 66 There is nothing in the judgment of the International Court of Justice to indicate that the Court was of the view that crimes under international law, which include the crime of torture, necessarily can be assimilated to acts committed in a “private capacity”.237 Added to the fact that the definition of torture in Article 1 requires an element of official involvement, the universal jurisdiction in Article 5 §2 against former State officials enjoying functional immunity may in fact be subject to severe limitations under international customary law, as interpreted by the International Court of Justice in Congo v. Belgium. In other words, if an act of torture in a particular case is considered to have been carried out in an official capacity, a former State representative accused of this act may in fact enjoy life-long immunity. Indeed, although the Court emphasised that immunity from jurisdiction does not mean impunity238, the end result in some cases may nevertheless amount to de facto life-long impunity. 3. THE PROHIBITION OF TORTURE AS A NORM OF JUS COGENS There are indications that the prohibition of torture, whether it is committed on a widespread and systematic basis, a crime against humanity, or committed against a single victim, constitutes a norm of jus cogens.239 The major distinguishing feature of the rule of jus cogens is its indelibility. It is a norm of customary law which cannot be set aside by treaty or acquiescence but only by the formation of a subsequent customary rule or another norm of jus cogens of contrary effect.240 The concept of jus cogens was accepted by the International Law Commission, and incorporated in the final draft on the law of treaties in 1966, Article 50 of which provides that: