 A full course could be dedicated to issues relating to the relationship between international law and domestic law, and to the application of international law in domestic law. Or rather, one could devote several courses to those issues, because they are different in every municipal legal order. And furthermore, it is a very practical topic, raising many different problems. And let me name just a few of them. To what extent can individuals or corporations rely on international law provisions to defeat the application of national laws? To what extent can you sue the public authorities, the government, for damages when the public authorities have acted in disregard of the international law obligations of the state? Can you rely on a treaty provision in order to claim the invalidity of an administrative decision affecting you, or even the invalidity of an act of parliament? Additionally, questions about the relationship between municipal law and international law also raise constitutional issues about the respective responsibilities of the executive and of the legislature in the making of treaties. And of course, all those questions receive different answers in the different states of the world. So in this course, I can only sketch out the problems and help you to understand them by teaching you how to look at those issues, rather than to teach you how to solve them. Well there are two ways to look at the issue of the relationship between international law and domestic law, or rather two perspectives from which that relationship can be viewed and explained. Either you look at that relationship from the point of view of international law, or you look at it from the point of view of the municipal legal order at stake. Let us start from the point of view of international law. From that perspective, things are quite easy to understand. From the point of view of international law, municipal law, domestic law, is a fact. Remember Article 27 of the Vienna Convention on the Law of Treaties? It is an axiomatic principle of international law that a state cannot rely on the provisions of its own domestic law as justification for its failure to perform its international law obligations. And the reasons for this is that the domestic law is the result of the own and unilateral will of the state concerned, and such will cannot validly defeat the performance of obligations resulting from the common will of various states. The only exception to that principle, you know, is the defect of consent based on Article 46 of the Vienna Convention. Knowing that domestic law is a fact from the point of view of international law does not mean that international law would deny the legal nature of domestic law. It simply means that the only question that arises under international law is whether domestic law is in conformity or not with the international obligations of the state. If the domestic law is not in conformity, then the state is responsible for a breach of its international obligations. The domestic law remains valid as a matter of domestic law, and the question is not to know whether it is valid or invalid under international law. The only issue is to know whether it is in fact compatible or not with what international law requires from the state which is the author of the Domestic Act at stake. In other words, from the point of view of international law, it is somehow a misnomer to say that in case of conflict between the rule of international law and the rule of domestic law, the rule of international law must prevail. And that's a misnomer because actually it is only if there is a real conflict between two norms, two rules, that one prevails over the other one. But domestic law has no normative status in international law. Domestic law is not a source of international law. Well true, when a comparative law exercise leads to the discovery of a general principle of law within the meaning of article 38 of the ICJ Statute, domestic law is duly taken into account in the formation of the rule of international law. But is this, of course, something completely different? And when the general principle exists, it exists as a rule of international law despite its domestic comparative law origin. In a case concerning certain German interests in Polish Upper Silesia, the Permanent Court of International Justice famously stated in 1926 that, I quote, From the standpoint of international law and of the court which is its organ, municipal laws are merely facts which express the will and constitute the activities of states. In the same manner as do legal decisions or administrative measures, the court is certainly not called upon to interpret the Polish law as such. But there is nothing to prevent the courts giving a judgment on the question whether or not in applying that law, Poland is acting in conformity with its obligations towards Germany under the Dżidniewa Convention at stake, end of quote. The fundamental logic of the relationship between domestic law and international law from the standpoint of international law has not changed since 1926, and it could not really be otherwise. Of course, international courts and tribunals pay attention to domestic law and sometimes they must refer to domestic law to decide on issues of international law. For instance, if a bilateral investment treaty gives rights to investors having the nationality of the parties, the investment tribunal's jurisdiction can be challenged by the respondent state by arguing that the person suing the state, the claimant, is not a national of the other contracting state protected under the treaty and therefore that it is not entitled to start the arbitral proceedings. In order to decide on that issue, the tribunal will have to turn to the domestic laws of the state relating to nationality. But in such a case, the domestic law issue will be somehow a preliminary question and will need to be looked at because the treaty provisions refers to the issue of nationality. And to take another example, where a domestic law issue can be relevant, if an international court has to decide on the international responsibility of a state and that the state contests that the person who acted was one of its civil servants, the tribunal or the court will have to look in the domestic rules of the state to see whether the person had an official status as agent of the state, etc. Now let's take a step to decide. Let's change from perspective and look at the relationship between international law and domestic law but from the point of view of domestic law.