1. University of Macerata 2014-2015 Prof. Avv. Roberto Baratta, PhD
International Organisations Law 5

2. Sources of international law
Ascertainment of the law in domestic legal orders is not usually too difficult a process (acts of Parliaments and how it has been interpreted by the courts). There is a certain degree of certainty in this legal process, given its hierarchical character
Contrast striking when one considers the situation under international law (IL). There is no one single body to create binding rules, nor a proper system of courts enjoying comprehensive and compulsory jurisdiction to apply IL
Yet IL does exist and is ascertainable

3. Definition of IL sources
= legal provisions binding and operating within the international legal order
ARTICLE 38 Statute of the ICJ is the most authoritative statement as to the sources of IL, though limited to the IL provisions the ICJ must apply. Definition widely accepted by international tribunals and arbitrators
- international treaties
- international custom as evidence of a general practice accepted as law
- the general principles of law as recognised by civil nations
- judicial decisions and the teaching of the most highly qualified publicists  it essentially operates as a simplified means to reconstruct the knowledge of IL

4. Custom
In any primitive society rules of behaviour emerge and prescribe the law. They are not written down and codified, but they have an aura of historical legitimacy
IL custom is a central source of law given that IL lacks a centralised authority. It is relatively a quite dynamic process since custom mirrors the contemporary concerns of society
Its imprecision means flexibility as well as ambiguity. It somehow reflects the inherent anarchical character of IL

5. Scope of customary law A widely recognized distinction:
General customary law
- rules of customary law that are of general application, valid for all States
Special customary law
- rules of customary law that are binding only on certain States only, i.e. regional or local custom.
- It is a practice accepted as law among a limited number of States, and as such it does not bind other parties. E.g.: a special regime may develop concerning the common frontier of two States; or among the limited number of States being part of a treaty

6. Dualistic nature of custom
Two constituent elements forging a custom
1. the material fact, the objective element, i.e. the actual behaviour of states and other subjects of IL (general practice or diuturnitas)
2. the psychological or subjective belief that such behaviour is law, is recognised as law (opinio juris sive necessitatis)
As the ICJ noted in the Libya/Malta case, the substance of customary law must be ‘looked for primarily in the actual practice and opinio juris of states’ (ICJ Reports 1985, p. 29)

7. General practice or material fact
Customary law is founded upon the performance of states activities and the convergences of practices.
State practice. As the ICJ consistently pointed out: it is ‘State practice from which customary law is derived’ (Germany v. Italy, ICJ Report 2012, para. 101)
The notion of practice includes physical and verbal actions (oral statements etc), as well as inaction or acquiescence
Attribution of practice to a State: the actions of all branches of Government (whether exercising executive, legislative, judicial or other functions) are relevant
The practice of intergovernmental institutions is relevant too. II as autonomous subjects of IL: their activities matter
There is no hierarchy among the various elements of practice

8. The objective element: requirements
Several main requirements:
- Duration  there is no rigid time element and it depends on the circumstances of the case: is it ‘instant’ customary law possible?
‘the passage of only a short period of time is not necessarily, or of itself, a bar to the formation of a new rule of customary international law’ .. Yet, ‘an indispensable requirement would be that within the period in question, short though it might be, State practice, including that of States whose interests are specially affected, should have been both extensively and uniform … and should moreover have occurred in such a way as to show a general recognition that a rule of law or legal obligation is involved’ (North Sea Continental Shelf, ICJ Reports, 1969, para. 74)

9. Objective element: other features
- Continuity, repetition and uniformity  constant and uniform usage practice by States; there must be some degree of uniformity amongst state practice before a custom comes into being
Custom should mirror the perceptions of the great majority of states. Universality is not required.
‘…practice from which it is possible to deduce a general custom is that of the generality of States and not of all of them’ (Barcelona Traction, ICJ Reports 1970, p. 330, separate opinion of Judge Ammoun)

10. ‘Persistent objector’ exception
It is widely held exception, supported by practice and scholars: a State having persistently objected to an emerging rule of customary law, and having maintained its objection after the rule is crystallized, is not bound by it
- A custom cannot be “invoked against Peru, which far from having by its attitude adhered to it, has on the contrary, repudiated it …” (ICJ, Colombian-Peruvian Asylum case, Reports 1950, p )
Inherently consensual nature of customary law? Not really
A) Once a rule of customary law has crystallized, the exception cannot be invoked
B) Persistent objection to be effective, it must be clearly expressed before the rule comes into being.
Still a theory hardly acceptable

11. Opinio juris sive necessitatis
It means that a state has behaved in a certain way because it thought it was under a legal obligation to act that way.
Opinio juris = legal conviction
sive necessitatis = as a necessity (to behave in a certain way to comply with an obligation)
Opinio juris differs a legal custom, a legal rule from a mere social usage. Acts of comity and courtesy, even if carried out as a matter of tradition, lie outside the scope of customary IL

12. Opinio juris: the theoretical counterargument
The vicious circle argument = how a new rule of customary IL can ever emerge if the relevant practice must be accompanied by a conviction that such a practice is already law? Thus, the creation of a custom is affected by a mistake during its formation
This is a theoretical argument, though logically quite convincing. However, in practice the subjective element of customary IL has not created major problems in its concrete application.
Moreover, a long standing approach of international arbitrators shows that the opinio juris is a constitutive element of customs. Fairly indicative is Article 38 ICJ Statute: customs are described as practice accepted as law. Besides, how could a mere usage differ from a legal custom?

13. Jus cogens
A special category of customary IL Definition: rules of jus cogens are legal norms ‘accepted and recognised by the international community of States as a whole’ as norms ‘from which no derogation is permitted and which can be modified only by subsequent norm of international law having the same character’ (Vienna Convention on the Law of Treaties, art. 53) It derives from custom and has a peremptory character. It is a substantive rule having a higher status, e.g.: outlawing of aggression and of genocide; prohibition of slavery, of racial discrimination and of torture. It expresses a superior and fundamental normative value of the international community as a whole No derogation is allowed by treaties since it can be revised by further developments of customary law only  that raises the issue concerning the relationship between customary rules and treaties

14. Treaties
In contrast to custom, treaties implies a more deliberate method of creating law they imply an express will of the participating parties to create law between them; they require the express consent of the contracting parties
A variety of different names describes a treaty, ranging from treaties, conventions, agreements, protocols, pacts, charters and so forth
Enormous amount of treaties exists, ranging from outer space exploration, control of drugs and so on. It would be impossible to telephone abroad or to take an airplane to other countries without international agreements
Bilateral or multilateral treaties, depending on the number of parties that ratified a given instrument

15. General principles of law
In any system of law a court may realise that there is no law covering exactly the point raised by the instant case, neither parliamentary law nor judicial precedent.
Such a situation is perhaps even more like to arise in IL because of its underdeveloped legal provisions
The ‘general principles of law recognised by civilised nations’ was inserted into Article 38 ICJ Statute to tackle such a situation. General principles are grounded in the actual practice of States. Hence, its customary nature
For instance, a general principle of law is that of pacta sunt servanda, or the idea that international agreements are binding; or the principle according to which treaties must be interpreted, applied and fulfilled in good faith.