Public International Law Notes - Sources of International Law

PIL: L2 – Sources of International Law

What are the Sources of International Law:
 What do we mean by ‘sources’ of international law?
 How do we discover what the law is? What is the law’s content?
 Domestic legal systems: where we found out what the law is.
- Law based on codes, statutes, regulations, case law, constitutions
- Hierarchy of norms
- Specified processes for the formation of law – EG: bills go through the houses of
parliament.
- Role of courts in stating what the law is
 International law:
- Decentralised system of law – no central law-making body – EG: no parliament,
no government.
- Plurality of norms – various different rules that are being applied side by side
- Various forms of norm creation – state practice, custom
- No appellate court or constitutional court – can go to the international court of
justice, but the decision of the court will only be binding on the parties
concerned.
 What about the ICJ? Judgments are only binding on the parties to the dispute

Formal Sources of International law:
 This can be found in Article 38 (1) Statute of the ICJ:
(1) The Court, whose function is to decide in accordance with international law such
disputes as are submitted to it, shall apply:
(a) international conventions, whether general or particular, establishing rules
expressly recognized by the contesting states;
(b) international custom, as evidence of a general practice accepted as law;
(c) the general principles of law recognized by civilized nations;
(d) subject to the provisions of Article 59, judicial decisions and the teachings of the
most highly qualified publicists of the various nations, as subsidiary means for the
determination of rules of law.
 This is a list of sources applied by the ICJ, but is recognised as the authoritative
sources of international law (because it is applied by the courts.)
 (d) – applies to article 59: “The decision of the Court has no binding force except
between the parties and in respect of that particular case.”
 Law creation process vs law determining process – is this a valid distinction?
 Interaction between formal sources of law. e.g. Treaties may reflect customary
international law; judgments of international courts may develop international law

Customary international law: “international custom, as evidence of a general practice
accepted as law”
 Customs are an authentic expression of the needs and values of a community at a
given time.
 Deduced from:
- Behaviour of states (state practice) and
- Intention of states (opinio juris)
 Represents a consensus approach to law making
 Who is involved in the creation of custom? Democratic process? Role of powerful
states?
 How to distinguish between legal custom and social usage?

,  How does one tell what motivated a state to act in a certain way?
 Practice must be uniform – something that all or nearly all states do.
- Asylum case (ICJ): customary law must be ‘in accordance with a constant and
uniform usage practised by the States in question”
 Court found that there was no constant and uniform usage which meant that no
custom had been established.
 Anglo-Norwegian Fisheries case (ICJ) – insufficient uniformity of state practice
 North Sea Continental Shelf cases (ICJ) – importance of states that are “specially
affected”
 What happens when a state doesn’t act in accordance to the rule, does this mean you
are establishing a new rule?
- New way of doing things, a new custom, therefore a new rule.
- Discussed in the Nicaragua Case
 Nicaragua case (ICJ) – practice inconsistent with a rule should be viewed as a
breach, not development of a new rule
 How widespread must the practice be? A majority of states? There is no numerical
criteria, but rather if the practice is uniform or not.
 At which point in time is a customary rule created? – EG: people walk across a park
and a path will eventually be created, but we can’t pinpoint it.
 Customary international law allows new development of the law BUT can take time
to change
 Some states may be particularly influential e.g. UK impact on law of the sea;
US/Russia impact on air/space law, and not all states involved in creation of rules
 Failure to act? This may also develop custom BUT Lotus case (PCIJ) – abstention
could amount to custom if there is a conscious duty to abstain.
 Which acts are considered ‘state practice’?
- Legislation, domestic judgments, treaties, military manuals, court decisions, acts
on the international plane (e.g. treaties)
- Acts carried out by state organs (diplomats, government officials, etc.) not
private bodies
- Actions in international affairs: UN General Assembly resolutions, statements,
voting patterns, comments made by governments on the work of the
International Law Commission
 Opinio juris - States’ belief that the act is legally obligatory – ‘a sense of obligation’
 North Sea Continental Shelf case – did a rule in the Geneva Convention on the
Continental Shelf (not binding on Germany) reflect customary international law at
the time?
 Court looked at practice during the negotiations of that instrument and subsequent
practice since it was adopted – did not reflect CIL
 How does customary international law change? If new practice is accepted/rejected
by other states. Acquiesce to new rules?
 Difficulty of demonstrating intent of states
 May also look at reactions by other states
 Work of international bodies in codifying international law (e.g. International Law
Commission)
 Customary international law may be reflected in international treaties, especially
codification treaties (e.g. UN Law of the Sea Convention)
 Resolutions of the UN General Assembly have taken on an important role in
developing custom e.g. principle of self-determination
 Persistent objector rule – a state opposing a rule is not bound by it