SOURCES OF INTERNATIONAL LAW*

A source of International law means those origins from where it attains its authority.

Types of sources

Formal sources Material sources

International lawyers draw a distinction between ‘formal’ and ‘material’ sources of law.
In other words a formal source is that from which a rule of law derives its force and validity
.The material sources supply the substance of the rule to which the formal sources give the
force and nature of law.

Formal sources are those giving a particular norm its validity or authority – treaty, custom
and general principles. Thus, the reason why the Nuclear Test Ban Treaty is legally binding
is that it is a norm laid down through the process of treaty-making. The prohibition on the
commission of crimes against humanity, and the rights and obligations relating to the
prosecution by states of offenders, is as a result of the existence of a rule of customary
international law on the issue

Material sources, on the other hand, reflect evidence that may be referred to in order to
prove that a particular norm has a formal source. For example, the UN Charter is a material
source that evidences the content of the important treaty law it represents. The practice of
states and their belief about that practice (opinio juris) are material sources for the
proposition that particular customary norms exist – indeed, they are critical elements that
establish the existence of such a norm. A piece of evidence can be used as a material source
without regard to whether the source is itself norm-creating. Hence, judicial decisions and
the writings of publicists, as subsidiary sources of law, can be relied upon to help form an
opinion about whether a rule exists.

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 International law differs from domestic law in that it is not always that easy to find out
what the law is on a particular matter. Domestic law is reasonably certain and found mostly
in legislation and judgments of a hierarchy of courts. In contrast, international law is not
so accessible, coherent or certain. There is no global legislature (the UN General Assembly
does not equate to a national legislature), and no formal hierarchy of international courts
and tribunals. As with the (mainly unwritten) British Constitution, an initial pointer to the
international law on a given topic is often best found in the textbooks. They will explain
that international law is derived from various sources, which are authoritatively listed in
Article 38(1) of the Statute of the International Court of Justice (annexed to the UN
Charter) as:

➢ Article 38(1) of the Statute of the International Court of Justice provides: The Court,
whose function is to decide in accordance with international law such disputes as are
submitted to it, shall apply:

International conventions, whether general or particular, establishing rules expressly

recognized by the contesting States;

International custom, as evidence of a general practice accepted as law;

The general principles of law recognized by civilized nations;

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.

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 1. International Treaties and Conventions
Treaties represent a source of law whose importance has grown since 1945.
Treaties may be bipartite/bilateral or multipartite/multilateral and they may create particular or
general rules of international law.
A distinction is often drawn between law-making treaties (traité-lois) and treaty contracts
(traité contracts).

Treaties

bipartite/bilateral or multipartite/multilateral

law-making treaties contracts

(traité-lois) (traité contracts)

The essence of the distinction lies in the fact that treaty contracts, being agreements between
relatively few states, can only create a particular obligation between the signatories, an obligation
which is capable of fulfilment, eg an agreement between France, Germany and the UK to develop
and build a new fighter jet.
A treaty is an express agreement under International Law entered into by actors in International
Law, namely sovereign states and International organizations. A treaty may also be known
as (International) agreement, protocol, Covenant, Convention, exchange of letters,
etc. Regardless of the terminology, all of these international agreements under International Law
are equally treaties and the rules are the same.

Law-making treaties create obligations which can continue as law, eg an agreement between 90
states to outlaw the use of torture. There has been a great increase in the number of law-making

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treaties throughout this century. One reason for this growth is the increase in the number of states
and the fact that many new states have a lack of faith in any rules of customary international law
in which they have not played a part in creating. The term ‘law-making’ can lead to confusion
and it should be used with care – strictly speaking no treaty can bind non-signatories. Even a
multipartite treaty only binds those states which are party to it. The mere fact that a large number
of states are party to a multilateral convention does not make it binding on nonparties although its
existence may be evidence of customary international law as was discussed in the North Sea
Continental Shelf cases (1969).
For this reason sometimes the term law-making is replaced by ‘normative’. Normative treaties
bind signatories as treaties, but may also provide evidence of rules of custom which bind all states.
Examples of normative treaties would include treaties operating a general standard setting
instrument – e.g. International Covenant on Civil and Political Rights 1966; and treaties creating
an internationally recognised regime – e.g. the Antarctic Treaty 1959.
Customary law and treaty law have equal authority. However if there is a conflict between the two
it is the treaty that prevails. This point is illustrated by the Wimbledon case (1923).
Pacta Sunt Servanda: According to this principle, ‘basis of all treaties are the binding obligation
annexed to it’. The binding effect of that rule rests in the last resort on the fundamental assumption
which is neither consensual nor necessarily legal, of the objective binding force of International
Law. The principle requires that ‘State are bound to fulfill in good faith the obligation assumed by
them under treaties’. The principle of sanctity of contracts is an essential condition of life of any
social community. No economic relation between States and foreign cooperation can exist without
this principle. It is a positive norm of International Law. In North Atlantic Fisheries case (1910)
the PCIJ pointed out the central position of the good faith people in the concept of pacta sunt
servanda. The binding force of treaties is evident from the fact that treaties are pieces of
international legislation and, therefore, possess legislative authority.
Article 26 and 27 of VCLT deals with this principle in totality. The requirement of good faith is
also inherent in the text of U.N. Charter, 1945.Thus perhaps the most fundamental principle of
treaties is pacta sunt servanda.
10. Exception to the principle: Although the principle is observed by the States in respect of all
the treaties, there are exceptions to this rule.
a.) When a new State comes into existence as a result of a revolt, it does not consider itself to
remain bound by the treaties concluded by the predecessor state. But it is not applicable for
boundaries agreement.
b.) If there is a fundamental changes in the circumstances which forms the core of treaty then such
treaty could unilaterally revoked by the parties or party.
11. VCLT, 1969: This convention deals with general principles of treaty, i.e. how the treaty is to
be interpreted on various aspects. It has come into force on Jan 27, 1980. It contains of 85 articles
which are divided into 5 parts. But it is applicable only over that treaty which is signed after the
entry into force of VCLT. The principles are: a.) Parties competent to make treaty, b.) Free consent
of the Parties; c.) Modes of expression of State’s consent; d.) Formation or conclusion of treaties;

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e.) Ratification of treaty (purpose of ratification, modes of ratification and refusal of ratification);
f.) Reservation to a treaty; and g.) Treaties and third States.
12. Jus cogens: These are those treaty norms from which no States could depart while concluding
the terms of the treaty. They form basic structures of International Law and are applicable to such
an extent that states are not allowed to make any reservation on these norms. There are no
exceptions to the said rule. Article 53, 64 and 66 forms jus cogens regime of the VCLT. A treaty
stand void if it is contrary to jus cogens norms

2. International Custom
First states simply did what they wanted to do, but when the contact between states
increased, certain norms of behavior turned into rules of customary law. Custom becomes
less importance as the legal system matures. Its contribution is still reflected in many treaties.
What is custom?
Custom is a practice followed by those concerned because they feel legally obliged to
behave in such a way. It is important that it is done out of legal obligation or a feeling
that violation would produce legal consequences.
Custom becomes law due to two elements

Material element Psychological element

Custom becomes law due to two elements:

Material element: the behavior and practice of states;

Psychological element: the subjective conviction held by states that the behavior in
question is compulsory and not discretionary.

(1) State practice

Custom needs to have those two elements in order to be custom. When a rule becomes
custom, it is called crystallization into customary law. The material element and
Psychological element There is no set time limit or duration of practice. This unimportance
of time is highlighted by the North Sea Continental Shelf cases. The length of time
required to establish the rule depends upon other factors. For example, if there is an existing

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rule that needs to be revised in order to make the new rule, it will take more time. Before
state practice can be considered as law, it needs to have a ‘constant and uniform usage’.
2.The psychological element; opinio juris
There must be a distinction between rules which are regarded as legally obligatory and those
which are discretionary. Opinio juris is the subjective belief maintained by states that a
particular practice is legally required of them. The original term is opinio juris sive
necessitates. The states must believe that the practice is obligatory and they must not think
that they are free to disregard at any moment. Opinio juris can be deduced from the
attitude of parties and states towards General Assembly Resolutions. The problem is that it
is different to say when a practice has turned into law. The state’s acceptance or recognition
to the binding character of the rule must be established.
Essential ingredients of a Custom: Following are the main ingredients of an international custom:
a.) Long Duration: In Article 38, emphasis is not given in a practice being repeated for a long
duration. What is more important is the practice of States accepting the practice concerned as law.
In the field of International Law, customs have emerged in a short duration, for e.g. custom relating
to sovereignty over air space and the continental shelf.
b.) Uniformity and Consistency: The custom should be uniform and consistent. Though complete
uniformity is not necessary, yet there must be substantial uniformity. In Pacquete Habana case
(US Supreme Court, 1990) the court examined State laws and practices, treaties, writings of
publicists evidencing usage, and decisions of court, and held that these materials uniformly proved
the existence of a valid customary rule giving immunity to small fishing vessels, honestly pursuing
their calling, from belligerent capture in time of war. (Asylum Case, ICJ 1950)
c.) Generality of Practice: Although universality of practice is not necessary, the practice should
have been generally observed or repeated by numerous States. Valid International customs should
be proved by satisfactory evidence that the custom is of such nature that it has received general
consent of the States and no civilized state shall oppose it (West Rand Central Gold Mining case,
1905). If a State acts in a way prima facie incompatible with a recognised rule, but defends its
conduct by appealing to exceptions or justifications contained within the rule itself, whether or not
the State’s conduct is in fact justifiable on that basis, the significance of that attitude is to confirm
rather than to weaken the rule. (Nicaragua case, ICJ 1986).
Application of International Customs – Difficulties: It is quite difficult to establish an
international custom before an international judicial tribunal, on account of the following reason:
i.) The very existence of a custom must be proved;
ii) It has to be established that the custom in question has had a continuous practice among a large
number of States, and that too consistently and without any break whatsoever or without any
variation in its practice;
iii) It is very difficult to prove opinio juris, a subjective element;
iv) The onus of proving the existence of an International custom lies on the State which seeks to rely
thereon. An International tribunal cannot assume the presence of such customs suo moto; and
v) The International custom must not run contrary to the rules of principles embodied in law-making
treaties, otherwise it will be superseded by the latter. (SS Lotus Case, PCIJ 1927 and The Right of Passage
Case, ICJ 1960).

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 3. The general principles of law recognized by civilized nations
Compared with domestic law, international law is relatively under-developed and patchy, though
in the last fifty years it has developed several important new specialised areas. International courts
and tribunals have always borrowed concepts from domestic law if they can be applied to relations
between states, and by this means have developed international law by filling gaps and
strengthening weak points. Such concepts are chiefly legal reasoning and analogies drawn from
private law.
Good faith
The obligation to act in good faith is a fundamental principle of international law, and includes
equity.Article 2(2) of the UN Charter requires all Members to fulfil their Charter obligations in
good faith. Similarly, the Vienna Convention on the Law of Treaties 1969 requires parties to a
treaty to perform the treaty (Article 26), and to interpret it (Article 31(1)), in good faith not
restricted to treaties but applies to all international obligations.

Estoppel
The principle is Known as preclusion in civil law systems, estoppel has two aspects. A state that
has taken a particular position may be under an obligation to act consistently with it on another
occasion. And when a state has acted to its detriment in relying on a formal declaration by another
state, the latter may be estopped from denying its responsibility for any adverse
consequences.Norms Sir Robert Jennings, a former President of the International Court of Justice,
once famously said that he would not recognise a norm if he met one in the street. But, some
international lawyers speak of norms of international law. In English, norm means a standard. Use
of the word seems to have been popularised by Professor Hans Kelsen, who saw international law
as at the top of the hierarchy of law. The term is used more by civil lawyers than common lawyers.
It may be useful in theoretical analysis of certain international law issues. principles and rules but
also lex ferenda ), but without a clear distinction being made between established law and
aspirations.
Equity
Amongst these general principles it could be argued that equity, in the sense of justice and fairness,
is included and in a number of cases it has been used indirectly to affect the way in which
substantive law is applied. The application of equity as a general principle should not be confused
with Article 38(2) which states that if both parties to a dispute agree, the court can decide a case
ex aequo et bono, ie the court can apply equity in precedence to all other legal rules.

Res Judicata: A matter once judicially decided is finally decided and there is an absolute bar to a
subsequent action involving the same claims, demands or cause of action. In U.N. Administrative
Tribunal case, 1954 certain members of the Secretariat of UN were discharged of their services by

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the Secretary General of UN. Consequently they filed the complaint, that such discharge was
illegal, before UN Administrative General. Some of the complaints were held justified and awards
in favor of such officials concerned were made.

One must come with clean hand: In Chorzow Factory case (PCIJ, 128), it was held that a party
cannot take advantage of its own wrong, a principle generally accepted in the jurisprudence of
international arbitration as well as by municipal courts.

Prescription (a claim to a right founded upon enjoyment): In Eastern Greenland case (1933,
PCIJ) bot Norway and Denmark claim their title over a part of the Greenland on the basis of
displayed sovereignty. Denmark contended that it exercised sovereignty over Greenland
peacefully and continuously for a long period. Norway maintained that at the time of it occupation
it was a no man’s land area and lay outside the limits of Danish colonies in Greenland. It was held
that a claim of sovereignty based not upon some act or title such as treaty of cession upon continued
display of authority involves two elements – the intention or will to act as a sovereign and some
actual exercises or display of such authority. The court held that Eastern Greenland was under the
sovereignty of Denmark. In Island of Palmas case (1928) both America and Netherlands claimed
sovereignty over the Island of Palmas. The arbitrator Huber, decided in favour of Netherlands on
the basis of unchallenged acts of peaceful display of sovereignty by Netherlands spread over the
period between 1700 to 1906.

Judicial decisions
Article 38(1) (d) of the Statute of the International Court of Justice directs the Court to apply
‘judicial decisions as subsidiary means for the determination of rules of law’. This direction is
made ‘subject to the provisions of Article 59’, which state that ‘the decision of the Court has no
binding force except between the parties and in respect of that particular case’. In other words,
there is no formal stare decisis doctrine, as known in common law systems; in international law
international courts are not obliged to follow previous decisions, although they almost always take
previous decisions into account. We have already seen that judicial and arbitral decisions can be
evidence of customary law. But it is probably true to say that judges can also create new law. The
International Court of Justice is particularly important in this respect.

Writings of publicists
The influence of academic writers has diminished markedly over the course of the history of
international law. Until the second half of the twentieth century, writers such as Grotius, Vattel,
Lauterpacht and Oppenheim were central to the development of an area of law that was mostly
customary and the subject of few treaties or judicial decisions. Indeed, these publicists were
instrumental in affirming and building the legitimacy of international law as a system of law.
However, with the increasing proliferation of international organizations, the development of a
world order based around the UN Charter, the explosion of treaty-making, the birth of sui generis
areas of law producing a breadth of judicial, administrative and quasi-judicial opinion (such as in

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the areas of human rights, trade, law of the sea and international criminal law) and the advent of
globalization, heralding technological change and a flatter, more interconnected world,
international courts and tribunals have seen less need for the opinions of publicists, which are often
tainted with bias. It is ironic that the growth of international law, which has contributed to the
proliferation of academic writing on international law, is also responsible for the diminution in
importance of such works as a material source of law.

Other sources of International Law

It has been said that, in the Nicaragua case, the International Court of Justice extensively referred
to resolutions of international organizations as a ‘source of law’, but under the particular
circumstances of the case concerning the issue of the jurisdiction of the Court, it is doubtful
whether it used these resolutions as sources in the technical sense. A resolution passed at a meeting
of an international organization is never conclusive evidence of customary law. It has to be
examined in conjunction with all the other available evidence of customary law, and it may thus
be possible to prove that the resolution is not a correct statement of customary law. In the end, if
there is no corresponding practice, the mere statement on what the law is supposed to be is not
sufficient evidence, but nothing more than an attempt on the part of states to clarify their respective
positions.
Nevertheless, as stated by the International Court of Justice in its 1996 Advisory Opinion on the
Legality of the Threat or Use of Nuclear Weapons with reference to the series of General
Assembly resolutions since that affirm the illegality of nuclear weapons:
General Assembly resolutions
General Assembly resolutions, even if they are not binding, may sometimes have normative
value. They can, in certain circumstances,provide evidence important for establishing the existence
of a rule or the emergence of an opinio juris. To establish whether this is true of a given General
Assembly resolution, it is necessary to look at its content and the conditions of its adoption; it is
also necessary to see whether an opinio juris exists as to its normative character. Or a series of
resolutions may show the gradual evolution of the opinio juris required for the establishment of a
new rule.
However, in view of the substantial numbers of negative votes and abstentions with which several
of the General Assembly resolutions on the illegality of nuclear weapons have been adopted, the
Court held that they still fall short of establishing the existence of an opinio juris on the illegality
of the use of such weapons.
Security Council Resolutions

The term ‘resolution’ has been used in United Nations (UN) practice in a generic sense, but it
includes broadly two kinds of statements: recommendations and decisions. When the International
Court of Justice (ICJ) refers to Security Council resolutions, it reserves the expression ‘decision’
for binding resolutions and ‘recommendation’ for non-binding ones. Security Council resolutions

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are generally only binding on the addressee, which may be one member, some members, all
members, or other UN organs. It can even be binding on ‘those members of the Security Council
which voted against it and those members of the United Nations who are not members of the
Council’. However, with regard to non-UN member states, Oberg has argued that the most
coherent interpretation of a difficult passage in the Namibia Opinion rejects any direct binding
effect. Therefore, it is argued that despite the ICJ statement in the Namibia opinion in that ‘it is for
non-member states to act in accordance (sic) with those decisions (of the UN Security Council)’,
that such resolutions are not binding on non-member states. In general, treaties only bind parties,
in accordance with the concept within international law that consent is required to be bound by
such obligations. Finally, since almost all States are now members of the UN, it would be hard to
find non-member States to be bound in this way.

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