International Judicial Monitor
Published by the American Society of International Law and the International Judicial Academy
April 2008 Issue

General Principles of International Law

Subsidiary Sources and Evidence of International Law

General Principles of International Law  

The Statute of the International Court of Justice recognizes two subsidiary means of establishing evidence of what is and what is not a binding international legal obligation. 

Case Law of Courts and Tribunals

“Judicial decisions” are the first of two specific “other sources” specifically mentioned in Article 38 of the Statute as a subsidiary means of determining the content of international law norms.  There is a wide body of case law from international courts and tribunals that can be examined—not to mention the decisions of domestic courts on international matters, including the identification of general principles of law accepted by civilized nations.  In this sense, while international tribunals do not normally follow the principle of stare decisis, previous judicial decisions can nonetheless play a significant—albeit subsidiary—role in developing the substance of international law.  

Teachings of Highly Qualified Publicists

The ICJ Statute specifically recognizes the “teachings of the most highly qualified publicists of the various nations” as evidence of rules of law.  In short, the writings of international law academics and practitioners — “publicists” in the language of the Statute — can constitute evidence of international law. In the United States, for instance, Supreme Court, as early as 1820, indicated that “the law of nations. . . may be ascertained by consulting the works of jurists, writing professionally on public law. . . .”  United States v. Smith, 18 U.S. (5 Wheat.) 153, 160-61 (1820).  “Such works are resorted to by judicial tribunals, not for the speculations of their authors concerning what the law ought to be, but for trustworthy evidence of what the law really is.”  The Paquete Habana, 175 U.S. at 699 (citing Ware v. Hylton, 3 U.S. (3 Dall.) 199, 226-27 (1796)).  

Equitable Principles

Equity is often mentioned as a subsidiary source of international law. To be sure, equity and fairness is a general principle of law recognized by all civilized legal systems, and would be incorporated into international law by that avenue.

Many equitable principles have been vigorously employed in international dispute settlement. One such concept is “abuse of right,” where an international actor is recognized as having the freedom to engage in certain conduct, but is barred from pursuing a course of action in certain circumstances or in a particular fashion.

Likewise, “unjust enrichment” has been used by international tribunals to give relief to an actor disadvantaged by a transaction, even though no formal contractual relationship existed.

Finally, the World Court has invoked the doctrine of “clean hands”—a party that seeks equity must do equity. Thus, in the Diversion of Water from the River Meuse,35 the Permanent Court of International Justice rejected mutual claims by The Netherlands and Belgium that each had impermissibly altered the flow of their boundary waters as each had altered the flow of the river.

There are two important caveats to the application of equitable or fairness doctrines in international law. The first is that equity does not mean reaching a result that is regarded as balanced—i.e., a judicial compromise. Such an outcome is the province of negotiation and mediation and is not regarded as being a legitimate application of a legal approach to dispute settlement.

In recognition of this, Article 38 of the ICJ Statute expressly bars the Court from deciding cases ex aequo et bono (“what is just and good”) unless the parties expressly agree to that. Similarly, equity does not mean equality. Despite strong efforts to fashion international law doctrines to serve the ends of distributional and social justice, international tribunals are not supposed to place judicial fingers on the scales in this fashion.

The Role of General Assembly Resolutions

There is no central legislature in international law, no World Parliament. While there is a growing network of international institutions producing a body of international regulatory schemes, these are all in the form of treaty regimes. Suggestions, therefore, that the resolutions of United Nations (UN) bodies (particularly the General Assembly, where each nation has one vote) constitute a binding source of international law are extravagant.

These intimations have been properly construed as an attempt to provide an easy way to make international law rules, apart from custom and treaty and without states’ consent to be bound. This is not to say, though, that the UN is powerless to make binding rules for its own operations. The question, instead, is whether General Assembly resolutions, which are only “recommendations” under Article 10 of the UN Charter, can make law.

One point that has often been made by commentators is that General Assembly resolutions, precisely because they are recommendations, lack the necessary opinio juris for custom.  This is so even though states may repeatedly vote for a resolution and profess their support for the legal rule it stands for. States, for example, overwhelmingly voted in the General Assembly for resolutions condemning state-sponsored torture, yet (as such groups as Amnesty International have reported) some of these same states actually engage in the torture of their own citizens.

Which do we prefer to believe: the professed position of the state, or the empirical evidence of its actual conduct? In some instances, international lawyers and judges will take states’ words at face value.

Learn More

International Law:  A Handbook for Judges, David J. Bederman with Christopher J. Borgen and David A. Martin, (2003) 

David J. Bederman, The Spirit of International Law (2002) 

Thomas M. Franck, Fairness in International Law and Institutions (1995)

Hersch Lauterpacht, The Development of International Law by the International Court (rep. 1982)

Mohamed Shahabuddeen, Precedent in the World Court (1996) 

(This text has been from excerpted and adapted from International Law: A Handbook for Judges, ©2003 American Society of International Law.)

35 (Neth. v. Belg.) 1937 P.C.I.J. (ser. A/B) No. 70 (June 28).


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