 You may recall the basic rule of the Law of Treaties, Pacta sun servanda. As article 26 of the Vienna Convention on the Law of Treaties reads, every treaty in force is binding upon the parties to it and must be performed by them in good faith. Observance of the treaty is owed by its parties from the moment it enters into force for each of them. You know that. It is not owed before that moment. However, it is possible that the parties to the treaty agree to apply the treaty or some of its provisions provisionally pending its entry into force. And this is because the ratifications procedures in every state may be a very lengthy process. Article 25 of the Vienna Convention provides for such possibility, a possibility which actually is quite common in practice, notably for treaties concluded by the European Union and its member states on the one hand with other states on the other hand. Of course the provisional application of a treaty with respect to a party is terminated if that party notifies the other parties that it does not intend to become a party to the treaty. Let me now recall another basic rule of international law that you know already. A state may not invoke the provisions of its internal law as justification for its failure to perform the treaty. As article 27 of the Vienna Convention also recalls, the only exception to that basic rule is article 46. That is a defect of consent consisting in the manifest breach of a domestic law provision relating to the competence to conclude treaties. You may remember that. Let me turn now to the temporal spatial and personal scopes of treaties. From a temporal point of view it is quite elementary in every legal system that as a matter of principle new rules only apply for the future and not to the past. And this is true also of the law of treaties and article 28 of the Vienna Convention provides for the principle of non-retroactivity of their provisions. A treaty does not bind a party in relation to any act or fact which took place or any situation which ceased to exist before the entry into force of the treaty for that party. Of course states may provide otherwise but this will remain exceptional and it must be made clear in the treaty. The rule on non-retroactivity also governs the temporal application of customary rules and of other sources of international law. From a spatial point of view now and as article 29 of the Vienna Convention puts it, I quote, a treaty is binding upon each party in respect of its entire territory. In other words the territorial sovereignty of states defines the scope of application of their respective treaties. And again this principle is not absolute and a different intention may appear from the treaty. For instance a treaty relating to the construction of a dam on an international watercourse may be applicable only to the section of the river where the dam must be built. Now from a personal or racioné-personé point of view the basic principle of Pactas und Cervanda explains that because any treaty must be performed in good faith by the parties to it, a contrario, a treaty does not create any right or any obligation for states or for international organizations that are not party to it. And this is made clear by article 34 of the Vienna Convention and this principle is called the relative effect of treaties which in domestic law would correspond to what is called the privity of contracts. But of course it is entirely possible if a non-party consents that a treaty confers to it a right or imposed on it an obligation. According to article 35 the third state must expressly accept the obligation in writing for such obligation to arise under a treaty to which it is not party. And in practice this is really really exceptional that states accept obligations imposed upon them by treaties to which they are not parties. According to article 36 the consent of the third state is presumed if the treaty confers a right to it but the treaty may nevertheless require express consent. And in exercising the right conferred to it under the treaty the third state must comply with the conditions for its exercise. The conditions for the exercise of the right are somehow obligations on the third state. Such conditions for the exercise of the right must extended to the third party can be provided for under the treaty or under other instruments deriving from it. And this is more frequent in practice and for instance the right of passage through the Suez Canal has been extended to the ships of all states under the Convention of Constantinople of 1888 which was however only concluded between eight European powers at the time and the Ottoman Empire. Of course and as we have already seen during the second week of this course when speaking about the borders of new states, state succession to border treaties is an exception to the rule according to which treaties are not binding on third states. And furthermore one should not forget that some treaty provisions may have a double nature. Any treaty provision is of course binding on the parties as a matter of treaty law but if the treaty provision also reflects a customary rule of international law its normative content will be binding on the third states as custom. An article 38 of the Vienna Convention recalls that. And if at some point in time the treaty terminates but the customary rule reflected in one of its provision continues to exist then all states including the parties to the terminated treaty all states will continue to be bound by that customary rule. And if the customary rule is well phrased well expressed by the treaty provision there is no reason not to continue to refer to it as a matter of convenience knowing of course that the words and sentences are those of a customary rule of international law not of a treaty.