Public International Law I
Sources of International Law
19 September 2013
Five distinct sources of law can be identified from Article 38 (1) of
the Statute of the ICJ which is generally taken to be the classic
statement of the sources of international law:
General principles of international law
The writing of the publicists
Equity a source additional also originates from Article 38.
However, the above list drafted more than 90 years ago (Article 38
reproduces the same article of the Statute of the PCIJ does not take
account of the evolution of international law)
Secondary legislation of the IGOs should be added to the above list.
It is debatable whether declarations made by a state or group of states
which produce binding legal effects are to be regarded as a distinct source
of international law.
Contemporary international law non-binding rules, the so called soft law,
which emanates from states and non-states actors, although not a source of
law, plays an increasingly important role in the international law making
Treaty can be defined as an agreement (usually written) between two or
more states, governed by international law and intended to create legal
Distinction between law making treaties (normative treaties) and treaty
Law making treaties lay down rules of general or universal application and
are intended for future and continuing observance.
Treaty contracts resemble contracts in that they are concluded to perform
contractual rather than normative functions (e.g. building an aircraft).
They are entered into between two or only a few states and deal with
particular matters concerning those states exclusively.
Such treaties like contract., expire when the parties have performed their
obligations (e.g. build the aircraft).
A customary rule requires the presence of two elements:
An objective element consisting of a relatively uniform and constant state
A psychological element consisting of the subjective conviction of a state
that it is legally bound to behave in a particular way in respect of a particular
type of situation. This element is usually referred to as the opinio juris sive
The objective element
This is normally constituted by the repetition of certain behavior on the part
of a state for a certain length of time which manifest a certain attitude,
without ambiguity, regarding a particular matter.
However, as no particular duration is required for practice to become law, on
some occasion instant customs come into existence.
For that reason, a few repetitions over a short period of time may suffice or
many over a long period of time or even no repetition at all in so far as an
instant custom is concerned.
However, the shorter the time, the more extensive the practice would have
to be to become law.
A practice must be constant and uniform, in particular with regard to the
affected states, but complete uniformity is not required.
It would suffice that conduct is generally consistent with the rule and that
instances of practice inconsistent with the rule are treated as breaches of
that rule rather than as recognition as a new rule.
So far as the generality of the practice is concerned, this will usually mean
widespread but not necessary universal adherence to the rule.
Indeed, custom may be either general or regional.
General customs apply to the international community as a whole.
Local or regional customs apply to a group of states or just two states in
their relations inter se.
The subjective element-opinio juris sive
To assume the status of customary international law the rule in question
must be regarded by states as being binding in law, i.e. that they are under
a legal obligation to obey it.
This is a sort of tautological statement i.e. state practice is not law unless
state consider it as law.
Nevertheless, the main purpose of the opinio juris sive necessitatis is to
distinguish between a customary rule and mere usage followed out of
courtesy or habit
The persistent objector rule
If during the formative stage of a rule of customary international law a state
persistently object to that developing rule it will not be bound by it.
This rule is known as the persistent objector rule.
Once a customary rule has to come into existence, it will apply to all states
except any persistent objectors.
However, as objecting state, on order to rely on the persistent objector rule,
Raise its objection at the formative stage of the rule in question;
Be consistent in maintaining its objection;
Inform other states of its objection. This is particularly important with regard
to a rule which has been almost universally accepted.
If a state remains silent, its silence will be interpreted as acquiescence to
the new rule.
The burden of proof is on the objective state.
The relationship between treaties and international
Relationship is complex.
They co-exist, develop each other, and sometimes clash.
If there is a clash between a customary rule and provision of a treaty then,
because they are of equal authority (except when the customary rule
involved is of a jus cogens nature) whereupon being superior it will prevail,
the one that is identified as being the lex specialis will prevail,
The lex specialis will be determined contextually.
Special rules of customary international law jus
cogens and rules creating erga omnes obligations
Jus cogens rules represent the highest source in the (informal) hierarchy of
sources of international law.
The emphasis of jus cogens obligations is on their recognition by the
international community ‘as a whole.’
The emphasis of erga omnes is on their nature. It mentioned embody moral
values which are of universal validity.
They are binding because they express moral absolutes from which no state
can claim an exemption whatever its political, economic and social
The legal consequences of violating erga omnes obligations differ from
those for breach of the rules of jus cogens
In addition to the consequences deriving from a breach of erga omnes
obligations further consequences, specified in Article 53 of the Vienna
Convention on the Law of Treaties, follow from violations of the rules of jus
General principles of international law
If there is no treaty relevant to a dispute or there is no rule of customary
international law that can be applied to it, the ICJ is directed under Article 38
of the Statute, to apply general principles of international law.
As there is no binding authority of precedent in international law,
international court and tribunal cases do not make law.
Judicial decisions are, therefore, strictly speaking not a formal source of law.
However, they clarify the existing law on the topic and may, in some
circumstances, create a new principle in international law.
They can also be considered evidence of state practice.
The writing of publicists
This source generally only constitutes evidence of customary law.
However, learned writings can also play a subsidiary role in developing new
rules of law.
This is a complex concept.
Under Article 38(1) (c) of the ICJ Statute equity is understood to be:
A general principle of international law and thus may be considered as a
material source of law.
A way of infusing elements of reasonableness and ‘individualized’ justice
whenever law leaves a margin of discretion to a court in deciding a case.
This is equity which operates within the boundaries of law (equity intra
Under Article 38 (2), equity means that a decision may be made ex aequo et
bono, i.e. the court should decide the case not on legal considerations but
solely on what is fair and reasonable in the circumstances of the case
(equity contra legem).
However, the parties must expressly authorize the court to decide a case ex
aequo et bono. So far, the ICJ has never delivered any judgment based on
Article 38 (2).
Secondary law of IGOs
There is disagreement whether secondary acts adopted by IGOs constitute
a source of law or whether, being a derivative source of law, they do not
form part of general international law.
It is important to make a distinction between primary and secondary law of
Primary laws refer to the founding treaties, i.e. treaty establishing the
Secondary law refer to acts adopted by IGOs on the basis of primary law.
Under traditional international law, secondary acts cannot be qualified as a
separate source of international law.
They are neither binding, nor abstract, nor general rules but derive from the
founding treaties, concern a specific area of law and produce legal effects
only in respect of member states of the relevant IGOs.
However the positivist approach has been challenged by the establishment
of IGOs having almost universal membership (e.g. UN) and by globalization
which entails not only the increasing interdependence of states but also the
need to find swift and appropriate solutions to new problems facing the
The better view, therefore, is that the secondary law of IGOs constitutes an
important source of international law.
Declarations-an uncertain source?
Whether a declaration by states is a source of international law depends on
the context in which it has been made.
It is debatable whether declarations which produce legal effects are a
source of international law.
Non-binding rules of international law are called ‘soft law’ whilst binding
rules are considered as ‘hard law.’
Soft law is of relevance and importance to the development of international
law because it:
Has the potential of law-making, i.e. it may be a starting point for later
‘hardening’ of non-binding provisions (e.g. UNGA resolution may be
translated into binding treaties);
2. May provide evidence of an existing customary rule’
May be formative of the opinio juris or a state practice that creates a new
4. May be helpful as a means of a purposive interpretation of international law;
5. May be incorporated within binding treaties but in provisions which the
parties do not intend to be binding;
6. May in other ways assist in the development and application of general
7. The importance of soft law is emphasized by the fact that not only states but
also non-state actors participate in the international law making process
through the creation of soft law.
Nevertheless. Soft law is made up of rules lacking binding force, and the
general view is that it should not be considered as an independent, formal
source despite the fact that it may produce significant legal effects.
Codification of International Law: The
contribution of the ILC
The ILC established by the GA of the UN in 1947 is made up of 34 legal
experts representing the world’s major legal system.
The two main task of the ILC are:
1. The codification of international law, which is defined as the more precise
formulation and systematization of the existing customary rules of
The progressive development of international law, which involves the
creation of new rules of international law either but means of the regulation
of a new topic or by means of the revision of the existing rules.
Since its inception the ILC has fulfilled its tasks with great professionalism
and dedication, producing numerous high quality international treaties,
declarations resolutions and model laws.