 You may remember that the grounds for invalidating a treaty are listed in the Vienna Convention and that those grounds are limited in numbers. Only the grounds listed in the Convention may be invoked in order to impeach the validity of a treaty. Under Article 42, paragraph 2 of the Vienna Convention, the same principle applies to the grounds that may serve to terminate, to withdraw from or to suspend treaties. It is important to say a few words on those issues after having elaborated a bit about the binding character of treaties. It is important because termination, withdrawal and suspension create situations where the treaty obligations are not owed anymore. Of course, when a treaty is lawfully terminated, the parties to the treaty are definitely relieved from the duty to perform it in its entirety. And the same is true for the party that has lawfully withdrawn from a treaty, even if what is called a sunset close will often differ the effect of the withdrawal notification for a certain period of time. Because of the limited scope of this course and because termination of treaties and withdrawal of a party most often take place in accordance with the provisions of the treaty, because of that I'm not going to dwell on all the grounds of termination or withdrawal. And besides, many of those grounds are quite obvious, clear and you may understand them by simply reading article 54 to 64 of the Vienna Convention. But rather I suggest to look more closely into two grounds that may serve either to terminate a treaty or to suspend its operation. Suspending the operation of a treaty is an interesting issue. In such a situation, the treaty is still in force and binding for the party invoking the suspension, but that party will be entitled not to perform the treaty temporarily. So compared with termination and with withdrawal, which result in parties not being bound anymore by the treaty, the consequence of suspension of the operation of a treaty is, as article 72 of the Vienna Convention puts it, and I quote, it is to release the parties between which the operation of the treaty is suspended from the obligation to perform the treaty in their mutual relations during the period of suspension, end of quote. But the suspension has no effect for the parties which are not affected by the suspension. During the time of suspension, the parties must refrain from acts tending to obstruct the resumption of the operation of the treaty. And this is indeed because suspension is only a temporary measure. Let me turn to those two grounds and look at them from the perspective of suspending the operation of a treaty. The first ground is provided for under article 60 of the Vienna Convention, which is entitled, I quote, termination or suspension of the operation of a treaty as a consequence of its breach, end of quote. It reflects a legal mechanism which is common to contract law in many national legal orders and which is expressed by the Latin maxim in a diplente non-est adiplento, or also excepcio non-adiplente contractus. This ground is probably the most commonly used when states want to justify the fact that they have not complied with their treaty obligations or intend not to comply anymore. The idea is very simple and based on reciprocity or quid pro quo, which is at the heart of any legal instrument based on the exchange of consent. A contracting party would say simply, I'm not performing this treaty because you have seriously breached it in the first place. In the readings that follow this video, you will have a chance to look more closely at the conditions set forth in article 60 of the Vienna Convention and to see the subtle technicalities of this legal mechanism in the law of treaties. Furthermore, the mechanism of in a diplente non-est adiplento, plendoom, sorry, is also used to justify human rights policies pursued through trade incentives. And this is called the policy of conditionality because trade benefits and access to market are conditioned upon the respect for fundamental human rights by the governments of the countries benefiting from such favorable trade access or other instruments of cooperation. And the European Union has notably inserted such conditionality in treaties concluded with developing countries and will see one prime example of such closures. The second grant I want to draw your attention to is less used in practice, but it is nevertheless important from a conceptual point of view. It relates to the impact of a fundamental change of circumstances on the duty to perform the treaty. Are those other treaty obligations still owed when the circumstance for their performance have radically changed from what was envisaged by the contracting parties? If performing the treaty becomes not impossible, but much more onerous, or that performing the treaty does not make the same sense because of the changed circumstances, must it still be performed? The issue is addressed by article 62 of the Vienna Convention, and of course there is a Latin maxim to express the principle. It is Rebus Sik Stantibus. After this video, readings will help you to understand what article 60 and 62 of the Vienna Convention are about.