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Sources of Public International Law 1

 Custom and Treaty as material Sources of International law


International law is a body of those laws governing the legal relations between nations. It has also been defined as the rules and principles of general application dealing with the conduct of nations and of international organizations and with their relations inter se, as well as with their relations with persons, whether natural or juridical. From  the Viewpoint of its sources international law is a body of consensual principles, which have evolved from customs and practices which civilized nations utilize in regulating their relationships and such customs have great moral force. Primarily, however, international customs and treaties are generally considered to be the most important sources of international law, as indicated in Article 38 of the Statute of International court of justice. Besides, there are some other sources of international law which are, mostly, indicated by international jurists. A detailed account of these sources is given below.


International Law has been variously defined by different international jurists.
(1) As defined by Oppenheim: “Law of Nations or International Law is the name for the body of customary and treaty rules which are considered legally binding by civilized states in their intercourse with each other.
(2) As stated by G.J. Starke: “International law may be defined as that body of law which is composed for its greater part of the principles and rules of conduct which states feel themselves bound to observe, and, therefore, do commonly observe in their relations with each other.”  


Source of Law connotes the origins from which particular positive laws derive their authority and coercive force; such as, customs, usages, constitutions, statutes, treaties. In another sense, the authoritative or reliable works, records, documents, edicts, etc., to which we are to look for an understanding of what constitutes the law. The same is the concept of the sources of international law. As pertinently stated by GJ.Starke: “By source of International law we mean the actual materials from which an international lawyer ascertains the rules applicable to a given situation.”  


The Statute of the International Court of Justice The relevant provisions of this statute are as follows:
1. Article 38 (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 customs, 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 laws. 
2.This provision shall not prejudice the power of the Court to decide a case ex aequo et bono,(what is right and good), if the parties agree thereto. Article 59. The decision of the court has no binding force except between the parties and in respect of that particular case.


(a) Definition: 

International treaty is an agreement, league or contract between two or mere nations or sovereigns formerly signed by commissioners properly authorized, and solemnly ratified by the several sovereigns or the supreme power of each state. It is not only a law but also a contract between two nations and must, 1f possible, be so construed , as to give full force and effect to all its parts. 

(b) Foundation: 

International lawyers use the phrase “Pacta Sunt Servanda ” to express the fundamental principle that agreements even between sovereign states, are to be respected. 

(c) Significance: 

International treaties are not only a principal source of international legal rules but are also themselves the subject of a considerable body of international law. The law of treaties serves much the same function in the international law as the law of contracts does in municipal law. 

(d) Treaty takes priority: 

There is no doubt about the fact that treaty stipulations override rules of international customary law which are incompatible with them. This proposition received approbation in the case of S S. Wimbledon (1923), where the permanent Court of international Justice held that treaty law takes priority over international customary law. 

(e) Kinds of Treaty: 

Treaties may be divided into four kinds, which stand as follows 

(i) Law-Making Treaty 

It lays down general rules binding on the states or enunciates new general rules for the guidance of the states in future or for their future international conducts.  

(ii) Treaty Contracts  

It deals with a special matter between the contracting states only. 

(iii) Bilateral Treaty  

It is a treaty which comprises only two parties and thus, is binding only on them. This treaty, usually, constitutes a treaty contract 

(iv) Multilateral Treaty 

If there are more than two parties in a treaty it is called multilateral treaty Usually, such treaty is also referred as a law making treaty, if it contains a considerable number of states. 

(1) Some Alternative names for treaty: 

Treaties are known by a variety of differing names;  
Conventions, International agreements, Pacts, General Acts, Final Acts, Acts, Concordat, Protocol, Charters, Statutes, Declarations and Covenants. 
All these terms refer to a similar transaction, the creation of written agreement whereby the states participating bind themselves legally to act in a particular way or to set up particular relations between themselves. 
(g) Important International Treaties:
Following are some instances of the important international treaties: 
i. Treaty of Westphalia (1648) 
ii. Paris (1815) and Versailles (1899) Charters 
iii. Geneva Conventions of 1864, 1906, 1929 and 1949  
iv. Hague Conventions of 1899 and 1907 
v. Covenant of League Of Nations ( 1920) 
vi. Charter of United Nations, 1945 
vii. Rome Treaty 1998, 2002 


(a) Definition:

Term ‘Custom’ generally implies to habitual practice or course of action that characteristically is repeated in like circumstances. 

(b) Custom and Usage: 

In order to understand custom it is necessary to know the meaning of the word “Usage". As pertinently explained by J.G.Starke “a usage is twilight stage of custom. “Usage is a repetition of acts, and thus, differs from “custom” in that the latter is the law or general rule which arises from such repetition, while there may be usage without custom, there cannot be a custom without a usage accompanying or proceeding it. 

(1) Significance: 

Article 38 (b) of the Statue of International Court of Justice recognizes international custom, as evidence of general practice accepted as law, as one of the sources of international law. For most modern international lawyers, customary international law is alongside treaty law, one of the two central forms of international  law. 

(d) Essential Elements of International Custom: 

Following elements constitute a valid international custom: 
(i) Duration: 
No particular duration is required nor does international court emphasize the time element as such in its practice. Provided the consistency and generality of a practice are proved. 
(ii) Uniformity and Consistency: 
Substantial uniformity and consistency of practice is required for a valid custom. 
(iii) Generality of the Practice  
As rightly remarked by Brownli, certainly universality is not required but the real problem is to determine the value of abstention from protest a substantial number of states in face of a practice followed by sonic others.”  
(iv) Opinio Juris et necessitates: 
The statute of the International Court refers to a general practice accepted as law, briefly speaks of recognition by states of a certain practice “as obligatory” and Hudson requires a “conception that the practice is required by, or consistent with, prevailing international law.” Some writers do not consider this psychological element to be a requirement for the formation of a custom, but it is, in fact, a necessary ingredient. 
(e) Judicial Application of Custom: 
According to GJ. Starke, “Both national and international courts play an important role in the application of custom. Often it is claimed by one of the parties before the court that a certain rule of customary international law exists. The Court must then investigate whether or not the rule invoked before it is validly established rule of international custom and in the course of this inquiry it examines all possible materials. 

(f) Evidences (Instances) of International Customs  

As enumerated by Brownli, “The material sources of custom are very numerous and include the following.
a. Diplomatic correspondence.  
b. Policy statements. 
c. Press releases. 
d. The opinions of official legal advisers.  
e. Official manuals on legal questions, e.g., manuals of military law, executive decisions and practices, order to naval forces etc. 
f. Comments by governments on drafts produced by the International Law Commission. 
g. State legislation.  
h. International and national judicial decisions.  
i. Recitals in treaties and other international instruments.  
j. A pattern of treaties in the same form. 
k. The practice of international organs.  
l. Resolutions relating to legal questions in the United Nations General Assembly. 

Further sources shall be posted soon on this blog according to the provisions of International court of justice.

Related Questions and searches:
This Article shall answer the following questions:
Write notes on Jus Cogen and international customs.
What are principle sources  of international law?
Explain customs and treaties as material sources of international law, as per Article 38 of the statute of International court of justice.


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