 Part 3 of the articles on the responsibility of states for internationally wrongful acts addresses the implementation of such responsibility. It is divided in two chapters, the first dealing with the invocation of the responsibility of a state and the second dealing with countermeasures as a way to implement such responsibility. Part 3 is probably the most conceptual part of the codification on state responsibility. It is also in that part that some of the most controversial issues are hidden when it comes to countermeasures. Let us take the articles as they stand and address in turn, as they do, the invocation of the responsibility and later countermeasure. As you will see, the two are of course intimately linked, but let us take things in the order. As far as the invocation of responsibility is concerned, the suma divisio introduced by the articles is between what is called in Article 42 the invocation of responsibility by an injured state and what is called in Article 48 the invocation of responsibility by I quote any state other than an injured state. This distinction intends to address a rather basic issue, which state has the legitimate interest to trigger the rules on international responsibility. Under Article 2 the injured state is defined as follows and I quote a state is entitled as an injured state to invoke the responsibility of another state if the obligation breached is out to a that state individually or b a group of states including that state or the international community as a whole and the breach of the obligation I specifically affects that states or double I is of such a character has radically to change the position of all the other states to which the obligation is owed with respect to the further performance of the obligation and of quote this is a fairly conceptual definition which requires some explanation of course even if the underlying issue is fairly straightforward and it is still to identify which states can lawfully claim to be the victim of an internationally wrongful act so as to officially require from all by all available legal means to require that the state responsible for the breach performs in its favor the new secondary obligations of cessation, reparation and eventually assurances and guarantees of non-repetition. In order to identify the injured or victim state the central issue is to determine to whom the obligation breached is owed. In Article 42 distinguishes between three possible cases. The first case is the easiest to understand it is when the obligation is owed to the injured state individually which means that the injured state has an individual right to the performance of the obligation breached. This is notably the case of obligations under bilateral treaties but this can also be the case under multilateral treaties or under customer international law and for instance the obligation under Article 22 of the Vienna Convention on diplomatic relations obligation to protect the diplomatic mission that is an obligation that each receiving state owes individually to each foreign state having a mission on its territory and the same is true for customer obligations relating to the immunity of states obligations that we will see and study in the course of next week. Likewise international obligations stemming from unilateral undertakings may be owed individually to states. The second and the third cases identified by Article 42 is when the obligation breached is owed I quote to a group of states including that state or the international community as a whole end of quote. The obligations that are here at stake can be owed to a group of states under a multilateral treaty or to the international community as a whole under a customary rule of international law. The obligations here at stake are called collective obligations in the sense that the performance of those obligations is not owed to one state in particular but to a collectivity a group of states or the international community as a whole. When the obligation is owed to the international community as a whole under a rule of customary international law the obligation is said to be erga omnes. The concept of obligation erga omnes was introduced by the International Court of Justice in the Barcelona Attraction case. The court having famously drew what she called an essential distinction between obligations owed to particular states and those owed towards the international community as a whole. And we shall come back to the notion of erga omnes obligations when speaking about states other than the injured state because as the court said in the Barcelona Attraction case I quote all states can be held to have a legal interest in their protection because of the importance of the rights involved. Examples of those obligations are human rights obligations or obligations to prevent the pollution of specific environments like the high seas. However, the violation of those collective obligations only injures a particular state if some additional requirements are met. Article 42BI refers to the case where the breach of the collective obligation which is thus an obligation not individually owed to any specific state when that breach I quote specifically affects a particular state. In such a case that specifically affected state will be considered as the injured state. The concept of being specially affected is taken from article 60 of the Vienna Convention on the Law of Treaties which relates you may remember to the exception of the one who has the full contract. It means that the breach of the collective obligation must affect a state in a way which distinguishes that state from the generality of the other states to which the obligation is owed. And for instance if a state party to the 1984 Convention against torture engages in torturing the national of another state party, well that other state party will be considered as specially affected and therefore injured. Or if an obligation to prevent the pollution of the sea is breached and pollution reaches the shores of a specific coastal state, well that state will be considered as specially affected and therefore injured. Under article 42BII the other possibility of being considered as an injured state when a collective obligation has been breached is when the obligation is I quote is of such a character as radically to change the position of all the other states to which the obligation is owed with respect to the further performance of the obligation end of quote. By this article 42 refers to a specific category of collective obligations called integral or interdependent obligations. They are to be found in for instance disarmament treaties, nuclear free zone treaties or treaties establishing specific regimes like the 1959 authentic treaty. In those cases the performance of each party is effectively conditioned upon the performance of each of the other parties and actually requires such performance by others. You may remember that those obligations are also mentioned under article 60 of the Vienna Convention on the Law of Treaties and their breach may trigger the right to terminate, suspend or withdraw from the treaty. But states may be more interested in keeping the treaty and in having the legal relationship restored by claiming cessation and reparation and that is why article 42 considers that when such interdependent obligation is breached every other state to which the obligation is owed will per se be considered as affected and therefore as injured.