Table of Contents

Introduction......................................................................................................................................2
Treaty Law.......................................................................................................................................2
(a) Law-Making Treaties........................................................................................................3
 Treaties enunciating the rules of Universal International Law -.......................................3
 Those enunciating general principles -.............................................................................3
(b) Treaty Contracts................................................................................................................3
Customary International Law..........................................................................................................3
i. Duration................................................................................................................................4
ii. Uniformity and consistency:.................................................................................................4
iii. Generality of Practice:......................................................................................................4
iv. Opinio juris ncessitatis:.....................................................................................................4
Importance of custom as a source of International Law..............................................................4
General Principles of Law recognised by Civilised States..............................................................5
Judicial Decisions............................................................................................................................6
Juristic Writings...............................................................................................................................7
Decisions or determinations of the organs of international institutions..........................................7
Jus Cogens.......................................................................................................................................7
Order of Sources of International Law............................................................................................8
Conclusion.......................................................................................................................................9
Bibliography..................................................................................................................................10
Introduction
International criminal law is a subset of public international law. While international law
typically concerns inter-state relations, international criminal law concerns individuals.
International Criminal Law (ICL) is a crucial aspect of global governance, aiming to address the
most heinous crimes that shock the conscience of humanity. It encompasses a set of principles,
norms, and mechanisms designed to hold individuals accountable for crimes such as genocide,
war crimes, crimes against humanity, and aggression. The foundation of ICL lies in various
sources that provide legitimacy, guidance, and enforcement mechanisms. This assignment delves
into the various sources of international criminal law.

As international criminal law is a subset of public international law, the sources of ICL are
largely the same as those of public international law, as follows:
 Treaty law;
 Customary international law (custom, customary law);
 General principles of law recognized by civilized states;
 Judicial decisions and arbitral awards (subsidiary source);
 Jurist Work (subsidiary source);
 Decisions or determinations of the organs of international institutions, and
 Jus Cogens

Treaty Law
The term “treaty” is used as a generic term embracing all kinds of international agreements
which are known by a variety of different names such as, conventions, pacts, general acts,
charters, statutes, declarations, covenants, protocol, as well as, the name agreements itself.
According to Article 38 of the Statute of International Court of Justice, it is the first source of
international law. In the modern period, international treaties are the most important sources of
international law.

As defined by Article 2 of Vienna Convention on the Law of Treaties, 1969, "a treaty is an
agreement whereby two or more States establish or seek to establish relationship between
them governed by international law." It may be noted that Vienna Convention of Treaties,
1969 entered into force on 27 January, 1980. As of January 2013, as many as 113 countries, even
those countries which are not parties to the Convention regard it as declaratory International
Law.

Fitzmaurice says that treaties are, formally, a source of obligation rather than a source of law.
They simply create rights and obligations. The only “law” that enters into these is derived, not
from the treaty creating them—or from any treaty—but from the principle pacta sunt servanda—
an antecedent general principle of law. The law is that the obligation must be carried out, but the
obligation is not, in itself, law. But as Holmes points out that whatever dignity treaties may lose
by not being “a formal source of law”, in practice they are a very, and increasingly, important
source of a State’s rights and duties.

International Treaties may be of following two types -

(a) Law-Making Treaties

Law-making treaties are those treaties which are entered into by a large number of
States. Such treaties have come into existence enormously since the middle of the 19th
century. Inadequacy of custom and emergence of new problems were responsible for
such law-making treaties. These treaties, in a sense, have produced international
legislation These are the direct sources of international law. Law-making Treaties may
be divided into following two types :
 Treaties enunciating the rules of Universal International Law -Those
treaties which are signed by a majority of the States are called the Treaties
enunciating the rules of universal international law. United Nations Charter is an
example of such type of treaties.
 Those enunciating general principles -Treaties which are entered into by a
large number of countries enunciated general principles of international law.
Geneva Conventions on the Law of the Sea and Vienna Convention on
Diplomatic Relations, 1961, are good examples of such types of treaties.
(b) Treaty Contracts
Treaty Contracts are those treaties which are entered into by two or more States. The
provisions of such treaties are binding only on the parties to the treaty. Such type of treaties
are also the source of international law because they help in the development of customary
rules of international law.

The International Military Tribunals and The Rome Statute (1988), which contain a list of
crimes and procedures for prosecuting them, are legal sources that have emerged directly
from treaty formulations. Additional legal sources include The Hague Convention (1907), the
Geneva Conventions (1949) and its additional protocols, the Genocide Convention (1949),
and The Torture Convention (1984). As a result of the formation of treaties, all of these
conventions were formed.

Customary International Law

International Customs used to be the most important source of international law in the past. In
the modern period, their importance has lessened. Custom is a habit which has been repeated for
a long time and has ultimately assumed the force of law. Usage is the earlier stage of the
development of custom. By usage we mean those habits which are often repeated by the States.
Custom begins where usage ends. Usages may be inconsistent and opposed to each other, but so
is not the case with custom. In the words of Viner, "A custom, in the intendment of law,
is such a usage as hath obtained the force of law." Customary rules of international law have
developed in the following three circumstances—(a) Diplomatic relations between States; (b)
Practice of Organs of International Institutions; and (c) State Laws, decisions of the State's
Courts and State's Parliamentary or administrative practices.

West Rand Central Gold Mining Co. Ltd. v. R., (1905) 2 K.B. 291 (Right of Passage over Indian
Territory Case) ; Portugal v. India, (I.C.J. Rep. 1960 at 6) and Paquete Havana, (1900) 175 U.S.
677 are good examples of application of custom in international law

Following are the main elements of an international custom :—

i. Duration: Long duration is an essential element of a custom in Municipal Law. But this
is not necessary for an international custom. Article 38 of the I.C.J. directs the world
court to apply international custom as evidence of a general practice accepted as law.
Thus 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 short duration, for
example, customs relating to sovereignty over air space and the sovereign rights over the
resources of the continental shelf.
ii. Uniformity and consistency: The custom should be uniform and consistent. But
complete uniformity is not necessary. Nevertheless, there must be substantial uniformity.
According to Tanaka and Sorensen JJ, it is often difficult to discover the necessary opinio
juris because the reason underlying a State’s adoption or acceptance of a particular
practice is not clear.
iii. Generality of Practice: Though universality of practice is not necessary, the practice
should have been generally observed or repeated by numerous States.
iv. Opinio juris ncessitatis: As pointed out by the International Court of Justice in
North Sea Continental Shelf cases, (I.C.J. Rep. 1969, p. 3), customary practice, even
when it is general and consistent, is not customary law unless an opinio juris is present,
that is to say, unless the practice is recognized as being required by international law. It is
this sense of law of legal obligation, as distinguished from motives of fairness,
convenience or morality, that underlies customary law."

Importance of custom as a source of International Law

There has been a marked decline in the importance of custom as a source of International law in
the modern times. This is mainly due to the fact that the process of development of a new custom
is very slow. However, in modern times also the development of new custom is possible and at
times customs have developed with accelerated speed. Principle relating to sovereignty over air
space and continental shelf are its glaring examples. But, in view of the accelerated speed of the
changes in International Community, custom has become an inadequate means for bringing
about the desired changes and development of international law. The development of custom is
very slow and as compared to it rapid changes can be made through treaties so as to adopt
International law in accordance with the changing times and circumstances. The four Geneva
Conventions on the Law of Sea (1958), Vienna Convention on the Law of Treaties (1969) and
U.N. Convention on Law of the Sea (1982), to quote only a few examples, bear testimony to this
fact.

In South West African case Judge Tanaka Observed : Briefly the method of generation of
customary international law is in the stage of transformation from being an individualistic
process to bring a collective process. This phenomenon can be said to be the adoption of the
collective process of international law to the reality of the growth of the organized international
community. It can be characterised, considered from the sociological viewpoint, as a transition
from a traditional custom making to international legislation by treaty. Thus, in the modern times
the importance of custom as a source of law has greatly reduced, with the simultaneous rise in
importance of treaties and conventions for the development of International law.

Thus, though the custom has been relegated to second place in importance, it still occupies an
important position as a source of law.

General Principles of Law recognised by Civilised States

The general principles of international law is the third source of international law recognised
under Article 38(1)(c). This provision comes into picture when other traditional sources, such as
the treaties or customary law does not provide a rule of decision. Unforeseen cases are bound to
be encountered, and in that case the judge would have to exercise discretion and adjudicate a
case on the basis of general principles of law recognized by a majority of nations around the
world. However, the term ‘general principles of international law as applied to the civil nations’
is vague, and many scholars have tried to interpret it. It has been debated for long whether or not
they constitute a valid source of international law. Professor Schlesinger refers to general
principles as “a core of legal ideas which are common to all civilized legal systems.” In
the North Sea Continental Shelf Cases, the ICJ opined that the term ‘civilized nations’ should not
be added as a legal element to evidence General Principles. Such a phrase would be
discriminatory and against the United Nations Charter that promotes the equality of all members
and non-members.

However, there are a few principles that have been employed by the courts while pronouncing
judgements. They can be considered as the general principles of international law:

 R. Key, (1876) 2 Ex. D. 63 - In this case the court ruled that international law is based on
justice, equity and good conscience which has been accepted by long practice of States.
  United States v. Schooner -In this case Justice Storey of United States of America ruled
that International Law should be based on the general principles of law recognized by
civilized States. He was giving decision relating to Abolition of System of Slavery.
 In the case of diversion of water from Muese, (1937) P.C.I.J. Series A/B, Fasc.No.70)
the Permanent Court of International Justice applied res judicata and estoppel.
 Chorzow Factory (Indemnity case), [Pub. P.C.I.J. (1938), Series A, No. 17).-In this case,
the Permanent Court of International Justice applied the principle of res judicata also held
that one who violates a rule is liable to make reparation.
 Mavrommatis Palestine Concessions Case, [Pub. P.C.I.J. (1924), Series A, No.2.1]-In
this case, the Court applied the general principle of subrogation.
 Case concerning the Temple of Preah Vihear, [I.C.J. Rep. 1962), p. 6 - In this case, the
International Court of Justice recognised and applied the principle of estoppel.
 Bracelona Traction Case, Preliminary Objections, (I.C.J. Rep. (1964), p. 6].—In this
case also the International Court of Justice applied the principle of estoppel.

As pointed out by B. Cheng, International Courts have recognised the following general
principles: i) good faith; ii) responsibility; (iii) prescription; (iv) in the absence of any
express provisions of the contrary, every court has a right to determine the limits of its own
jurisdiction; (v) a party to a dispute cannot himself be an arbitrator or judge; (vi) res
judicata; (vii) in any judicial proceeding, the court shall give proper and equal opportunity of
hearing to both parties. These principles should be codified.

Judicial Decisions
These are the subsidiary or secondary sources of international law that are regarded as the
interpretations of the primary sources. They are recognised under Article 38(1)(d) of the Statute
of the International Court of Justice. In the realm of international law, the decisions of
international courts and tribunals contribute significantly to the development of norms, the
clarification of legal ambiguities. This can be achieved in two ways: first, when the courts affirm
the existing principle of international criminal law by pointing out the practice and preexisting
opinio juris and secondly, by trying to declare a norm as custom through their decisions. The
courts tend to create new “customary rules” deducing them directly from “elementary
considerations of humanity”. Under the shield of humanity, they give decisions with the
expectation that the state’s practice will fall into the newly judge-made law. International
criminal tribunals, including the ICTY and the ICC, have played a pivotal role in prosecuting
individuals for genocide, war crimes, crimes against humanity, and aggression. Their decisions
establish precedents for defining and adjudicating international crimes, holding perpetrators
accountable, and providing justice to victims.

However, according to Article 59, the decisions of the ICJ are not binding, except on the parties
involved and in respect of that particular case only. Thus, the doctrine of precedent that is
applicable in the national courts, is not applicable in the international courts. Therefore, their
effectiveness is contingent upon state consent and cooperation, and challenges like enforcement
and legitimacy persist. Nonetheless, judicial decisions remain vital in advancing justice,
accountability, and the rule of law on the global stage.

Juristic Writings
The opinions of jurists are also regarded as sources of International Law. But, they are also
subsidiary means for the determinations of the rules of international law. Brierly opined that two
important functions performed by jurists are:
 They provide useful evidence of what the law is. This function is universally recognised.
 Another function is speculations concerning what the law ought to be, for their writings
may help to create opinion which may influence the conduct of states and thus indirectly
over time help to modify the actual law. Whether the speculations of any particular
author are likely to have this active influence depends mainly on his prestige and on the
persuasiveness with which he presents his arguments.

Justice Gray of the United States Supreme Court has observed in the Paquete Habana case that:
“Where there is no treaty and no controlling executive or legislative act or judicial decisions,
resort must be had to the customs and usages of civilised nations, and, as evidence of these, to
the works of the jurists and commentators, who by years of labour, research and experience have
made themselves peculiarly well acquainted with the subjects of which they treat. Such works
are resorted to by judicial tribunals, not for the speculations of their author concerning what the
law ought to be, but for trustworthy evidence of what the law is.”

Decisions or determinations of the organs of international institutions

This source, i.e. Decisions or determinations of the organs of the international institution is not
mentioned in Article 38(1) of the statute of the Court because it was not an important source of
International Law at that time when the Statute of ICJ was adopted. However, today it has
become a well recognised source.The United Nations has six principal organs and various
specialised agencies such as the World Health Organisation (WHO), (dealing with health
problems), International Labour Organisation (ILO), (dealing with labour problems),
International Civil Aviation Organisation (ICAO), (regulates the relation of states about
international civil aviation), Food and Agriculture Organisation (FAO), etc. Any decision taken
by any one of them is also a source of international law.

Jus Cogens
Jus cogen means a body of peremptory principles or norms which are authoritative in nature and
about which there is no controversy and from which no derogation is permitted. Article 53 of the
Vienna Convention on the Law of Treaties, 1969 defines a peremptory norm of general
International Law as a norm accepted and recognised by the international community of States as
a whole from which no derogation is permitted and which can be modified only by a subsequent
norm of general International Law having the same character. Further, Article 26 of the Vienna
Convention on the Law of Treaties gives two such generally acceptable norms i.e., the
prohibition against the threat or use of force mentioned in Article 2(4) of the United Nations
Charter, and the principle of Pacta Sunt Servanda (treaties to be respected in good faith).

Order of Sources of International Law

Though various sources of International Law are given a moot question is whenever a case is to
be decided by the International Tribunal in which order these sources must be followed and
applied? Various jurists like Oppenheim, Lawrence, Brierly, and Starke gave preference to
custom as a source of International Law. However, under Article 38(1) of the Statute of the
International Court of justice, sources of International Law are mentioned in the following order:
(a) International Conventions, (b) Customs, (c) General principles of law recognized by civilized
nations, (d) judicial decisions and juristic opinion as subsidiary means for the determination of
rules of law. Some jurists believe that the wordings of Article 38 suggest that sources are to be
applied in the order in which they are mentioned and therefore treaties will take precedence over
the other sources. Brownlie believed that the priority of application depends upon the order (a) to
(d) under Article 38(1) but it is unwise to think in terms of hierarchy directed by the order (a) to
(d) in all the cases.

However, according to Manley O. Hudson, “Article 38 did not establish a rigid hierarchy. In
applying a provision in a convention, the court may have to take into account the customary law
prevailing when the convention was entered into, or general principles of law, as well as judicial
precedents. A distinction may also have to be drawn between the categories listed, for they are
not on an equal footing while it is possible to apply the conventional or customary rule of law, it
seems more proper to say that the general principle of law, judicial precedents, and juristic
writings have only the nature of sources from which an applicable the rule may be deduced.”
Further in Nicaragua v U.S.A., the World Court by the majority has taken the view that the
sources of International Law are not hierarchical but are necessarily complementary and
interrelated.
Conclusion
International criminal law derives its authority and legitimacy from a diverse array of sources,
ranging from treaties and conventions to customary practices and ethical principles. The
evolution of this legal framework reflects humanity's collective endeavor to address the most
egregious violations of human rights and humanitarian law. However, challenges persist,
including the enforcement of judgments, ensuring universal adherence to legal norms, and
addressing the root causes of conflict and impunity. Despite these challenges, the sources of
international criminal law continue to serve as pillars of accountability, striving to bring
perpetrators to justice and uphold the fundamental values of humanity on a global scale. In
conclusion, the study of these sources offers valuable insights into the development,
interpretation, and enforcement of international criminal law, contributing to the ongoing quest
for a more just and peaceful world order.
Bibliography

Sources of international law: custom, treaties,general principles and judicial decisions. (n.d.).
Retrieved April 25, 2024, from Law, University of Jammu Kashmir:
https://law.uok.edu.in/Files/5ce6c765-c013-446c-b6ac-b9de496f8751/Custom/UNIT_II.pdf

Gomber, P. N. (n.d.). General Principals of law. Retrieved April 26, 2024, from e-adhyayan:
https://ebooks.inflibnet.ac.in/hrdp02/chapter/general-principals-of-law/

Joshi, P. (2019). International Law and Human Rights (4th ed.). Lucknow: EBC Publishing (P).
Ltd.

Kapoor, D. (2021). International Law & Human Rights (Nutshell) (18th ed.). Prayagraj: Central
Law Agency.

Panda, S. (2020, December 11). Sources of International Law. Retrieved April 24, 2024, from
iPleaders: https://blog.ipleaders.in/sources-international-law-3/

Raman, P. R. (n.d.). Fundamental of International Criminal Justice II (Sources). Retrieved April

23, 2024, from INFLIBINET CENTRE:
https://epgp.inflibnet.ac.in/epgpdata/uploads/epgp_content/human_rights_and_duties/
15._international_criminal_justice/02._fundamentals_of_international_criminal_justice-
_ii_(sources)/et/8257_et_02_et.pdf

Rattan, D. R. (2022). Public International Law (7th ed.). New Delhi: Bharat Law House Pvt.
Ltd.

Talawar, N. (2022, June 18). International Criminal Law. Retrieved April 26, 2024, from
iPleaders: https://blog.ipleaders.in/international-criminal-law/

What is International Criminal Law? (2018, March). Retrieved April 24, 2024, from Institute for
International Criminal Investigations (IICI):
https://iici.global/0.5.1/wp-content/uploads/2018/03/icls-training-materials-sec-2-what-is-intl-
law2.pdf