1. Ole Kr. Fauchald16.05.20151 Customary law – basic issues n Basic features of customary law ä No procedure or formalities related to adoption ä Lack of clarity regarding conditions for existence ä Lack of clarity regarding the content of rules ä Recent developments in the ways states communicate n Natural law and positivist perspectives on customary law ä Positivist: Consent: State practice, opinio juris and persistent objector ä Natural law: Jus cogens, general principles, universality

2. Ole Kr. Fauchald16.05.20152 Elements of customary law I n ICJ Statute art. 38: “as evidence of a general practice accepted as law” ä When does “custom” attain the status of “customary law”? n Practice – objective element ä How long-lasting? ICJ Fisheries case, Reports 1951, North Sea continental shelf case, Reports 1969 ä How uniform? ICJ Nicaragua case, Reports 1986 ä How wide-spread? ICJ Asylum case, Reports 1950 ä Minimum requirements or overall assessment? ICJ North Sea continental shelf case, Reports 1969 ä What constitutes evidence of State practice?

3. Ole Kr. Fauchald16.05.20153 Elements of customary law II n Opinio juris – subjective element ä Is this a mandatory requirement? ä Exclude the relevance of certain kinds of practice? ICJ Asylum case ä What constitutes evidence of opinio juris? n Emphasis on practice or opinio juris? ä Practice: slow and grounded development ä Opinio juris: faster and more politically oriented development ä Persistent objector

4. Ole Kr. Fauchald16.05.20154 Substantive rules of customary int’l law n Jus cogens ä Illegality of genocide, torture, ethnic cleansing, … n Fundamental principles of int’l law ä Art. 2 of UN Charter ä Declaration on Friendly Relations ä Declaration on Human Rights ä Rio Declaration on Environment and Development n “Secondary rules” ä The law of treaties ä State responsibility for unlawful acts, ILC Draft Articles n Other examples ä Rules on expropriation ä The obligation to prevent harmful activities

5. Ole Kr. Fauchald16.05.20155 Customary law and treaties n To what extent are treaties codification of customary law? ä The role of the International Law Commission and the UN General Assembly n To what extent can treaties exempt from rules of customary law? n To what extent can customary law exempt from treaties? n To what extent does customary law contribute to the interpretation of treaties?

6. Ole Kr. Fauchald16.05.20156 Customary law and general principles n The issue of ”non liquet” ä Rejection of ”non liquet” as an option for the ICJ ä But: Obligation to negotiate: ICJ North Sea continental shelf case, Reports 1969 n The issue of formal requirements for customary law ä Not the same requirements for general principles? n The relationship between international law and domestic law ä Borrowing from the domestic systems – ICJ Barcelona Traction, Reports 1970