 The principle of systemic integration leads to interpret different rules of international law in a harmonious way. Therefore, it promotes the avoidance of conflict between international obligations. However, harmonious interpretation is not always possible, so that situations exist where a state is facing conflicting obligations. It will be impossible for that state to perform one obligation without breaching another one at the same time. In such a situation, which obligation should prevail, which obligation should be preferred? Before answering that question, it is important to set aside what could be called fake situations of conflict between obligations. Situations where two irreconcilable obligations are not owed at the same time by the same subject. Most obviously, and I'm just repeating here things that you know already, most obviously there is no conflicting obligations when a treaty derogates from a general rule of customer international law. The treaty obligations will be owed between the parties to the treaty, while the parties will have to respect the customer rule in their relations with third parties. And most of the time, the principle of systemic integration will also help to accommodate the coexistence between the treaty obligations on the one hand and the customer rule on the other. Furthermore, no situation of conflict between obligations exists in the rather hypothetical case where a treaty is void because it conflicts with the peremptory norm of general international law. Because the treaty will be void, no obligation will be owed under the treaty and no conflict of obligations will exist. In such a situation, there is of course a conflict between two sources of international law, but such conflict does not result in a conflict of obligations between the obligations under the treaty will not be owed since the treaty will lack validity. Another fake conflict situation exists when all the parties to a treaty later conclude another treaty relating to the same subject matter. And that all the provisions of the new treaty are so far incompatible with the earlier treaty that the two treaties as a whole cannot be applied at the same time. In such a situation, and as recalled by article 59 of the Vienna Convention, in such a situation the old treaty is terminated and the parties must only apply the new treaty. Because the parties to the two treaties are identical, this does not raise any problem. If that is the case, there would be no conflicting obligations because the obligations under the old treaty are not owed anymore and have been replaced by the obligations under the new treaty. So it is important to keep in mind that a real situation of conflicting obligations requires that several valid obligations be simultaneously owed by the same subject, but that those obligations cannot be performed at the same time because performing one entails the violation of the other one. Situations of conflict, true situations of conflict between international obligations are not frequent in practice, but they may nevertheless exist most notably between treaty obligations. And those conflicts arise essentially because the production of international law, as you know, is not a centralized process. In case of conflicting obligations, one possible solution is to consider that one obligation prevails over the other one. The obligation being overruled is not void, but it is simply set aside as long as the conflict remains. And this is what Article 103 of the United Nations Charter provides for. Under Article 103, obligations of the UN member states under the Charter prevail over their obligations under any other international agreement. In other words, the Charter and the obligations arising under the Charter, and notably as we shall see at the end of the course, notably the obligations imposed by the Security Council through binding resolutions, those UN obligations endure hierarchical supremacy. Paragraph 1 of Article 30 of the Vienna Convention and Article 30 is the provision of the Convention about conflicting obligations. Paragraph 1 of Article 30 refers to Article 103 of the UN Charter. No other treaty but the Charter and the obligations flowing from it enjoy a similar and automatic supremacy. And of course, if several treaties had a similar legal supremacy, the very notion of supremacy would run into trouble. Another possibility is that to use the word of Article 30 paragraph 2 of the Vienna Convention, I quote, a treaty specifies that it is subject to or that it is not to be considered as incompatible with an earlier or a later treaty. If that is the case, then the provisions of the earlier or later treaty prevail, depending on the choice made. And such a situation is actually not uncommon in practice. For instance, under Article 351 of the treaty on the functioning of the European Union, treaties concluded by EU member states with third states before they acceded to the Union are said to be not affected by the EU treaties. And this means concretely that EU member states can validly disobey its EU obligations. If that is needed in order to perform a treaty, it concluded with a third state before joining the Union. However, the member state is also bound under Article 351 to, I quote, take all appropriate steps to eliminate the incompatibilities between the obligations under the pre-accession treaty concluded with the third state and the obligations under EU law. The duty to eliminate the conflict between those two types of obligations has been interpreted by the European Court of Justice as requiring that the pre-accession treaty be terminated by the member state if such possibility exists under international law. And of course the termination of the pre-accession treaty puts an end to any conflict of obligations. In other treaties, the preference for one treaty is expressed by a provision declaring that the application of the treaty cannot be impeded by other agreements. And for instance, under Article 91 of the Cottonoo Agreement establishing a partnership between the EU and its member states on the one hand and ACP countries, Cottonoo Agreement that you know, the contracting parties declare that, I quote, no treaty convention agreement or arrangement of any kind between one or more member state of the union and one or more ACP states may impede the implementation of this agreement, end of quote. Sometimes a treaty contains a commitment not to conclude agreements that would conflict with the treaty. And for instance, under Article 8 of the Washington Treaty of 1949 which established the North Atlantic Treaty Organization, NATO member states undertook under that article, I quote, not to enter into any international engagement in conflict with this treaty, end of quote. And such commitment can be interpreted as a conflict rule from the point of view of the members of NATO. In all those cases, it is not too difficult to decide which obligation must prevail. But what happens when there is no conflict rule inserted in one of the conflicting treaties? Well, that is the question we'll address in the next video.