International Judicial Monitor
Published by the International Judicial Academy, Washington, D.C., with assistance from the
American Society of International Law

Winter 2015 Issue

General Principles of International Law


Distinguishing Equitable Principles from Ex Aequo et Bono in International Law

Carolyn A. Dubay

By: Carolyn A. Dubay, Associate Editor, International Judicial Monitor and Assistant Professor of Law, Charlotte Law School

Most common lawyers are familiar with the equitable maxims that guide judges in adjudicating disputes and dispensing “justice.”  Law students learn that “equity will not suffer a wrong without a remedy” and that “he who comes into equity must come with clean hands.”  The role of equitable principles in international law, however, remains an area of debate and confusion. Part of this confusion results from the distinction between an international court’s application of generally accepted equitable principles (such as the doctrines of estoppel, unjust enrichment or unclean hands) and a judge’s decision to render a just decision ex aequo et bono – a decision arising from the judge’s own sense of “equity and conscience.” 

The distinction between equitable legal principles and ex aequo et bono is embedded, at least implicitly, in Article 38 of the ICJ (International Court of Justice) Statute.  Article 38(1) defines “international law” to include “general principles of law recognized by civilized nations.”  Time-honored equitable maxims that have been historically and routinely recognized and applied by courts in most common law countries certainly fall within general principles of law.  In civil law countries, these principles may be reflected in codified rules. On the other hand, Article 38(2) allows resort to ex aequo et bono only “if the parties agree thereto.”  The critical difference between equitable principles that may be recognized as “general principles of law” and ex aequo et bono is that decisions with reference traditional equitable rules are still considered as rendered within the framework of the law (either as infra or infra legem). Resort to ex aequo et bono, on the other hand, is considered to operate outside or even contrary to legal principles and reasoning (contra legem). In this regard, ex aequo et bono is not intended to fill gaps in the law (lacunae) to help interpret existing legal rules (praeter legem).  Rather, it is permitted or invoked to grant the judge free-floating discretion to do “equity” in any way possible, regardless of the strictures of legal rules.

There are several important reasons for the restriction on resort to ex aequo et bono adjudication in formal international judicial bodies.  First, the continued legitimacy of international judicial bodies depends on the consent of sovereign nations to operate within an international legal order.  To the extent that international judges abandon application of generally accepted legal principles in favor of their own personal preferences as to what is “just” notwithstanding those rules, the stability and predictability of the rule of law is jeopardized. In other words, the application of personal preferences and values, unbounded by legal rules or established principles, could lead to unpredictable results and instability in the legal order. Second, there is a recognized, although often debated, divide between equity as applied to do justice in legal disputes and the concept of fairness and equality in economic and political philosophy. The former is the realm of judges, while the latter is the realm of law-makers and political actors. Where exactly the dividing line falls between use of equitable principles and resort to ex aequo et bono can often be blurred.  Third, it is argued that dispute resolution ex aequo et bono lies properly in the realm of arbitration, conciliation


and mediation as a means to quickly and fairly resolve a dispute rather than resort to formal legal proceedings.  For this reason, the ICJ has never resorted to decision-making ex acqueo et bono, yet there are examples of such decision-making in international arbitration.

Despite the controversy over the judicial use of ex acqueo et bono, the invocation of “equity” as a principle of international law in international dispute resolution has ebbed and flowed over the last century.  As explained by famed international law scholar Professor Louis Sohn:

Equity was used frequently in international law during the 19th century.  Many international arbitrations provided for decision according to international law and equity. Then somehow at the beginning of the 20th century things quieted down and equity was used much less . . . . The [World] Court would state it was well known that a particular principle existed as a general principle of international law accepted by most nations and then would apply it, never mentioning equity.  In the 1960s when the Court began to consider disputes related to maritime boundaries in the North Sea Continental Shelf Cases, it rediscovered equitable principles . . .  Of course, in the North Seas Continental Shelf Cases and a number of following cases, various problems arose about what is equity, what are “equitable principles,” and third, what is an equitable result.[1]

In many ways, the ICJ’s 1969 decision in the North Sea Continental Shelf Case is emblematic of the use of equitable principles in international law, even if not grounded in a specific equitable doctrine used in domestic courts.  Whether resort to generalized equitable considerations amounts to adjudication ex acqueo et bono in a particular case can be debated. But like many courts, the ICJ in the North Sea Continental Shelf case carefully defined resort to equity not as a “matter of abstract justice, but of applying a rule of law which itself requires the application of equitable principles.” Judgment, at 47.  As the Court went on to state, “[w]hatever the legal reasoning of a court of justice, its decisions must by definition be just, and therefore in that sense equitable. Nevertheless, when mention is made of a court dispensing justice or declaring the law, what is meant is that the decision finds its objective justification in considerations lying not outside but within the rules, and in this field it is precisely a rule of law that calls for the application of equitable principles.  There is consequently no question in this case of any decision ex aequo et bono . . .”  North Sea Continental Shelf Case, Judgment at 48.

Ultimately, the lesson from the North Sea Continental Shelf case may be that when international or domestic judges perceive a threat to their legitimacy through reference to particular rules or influences in their decision-making, they will ultimately err in favor of preserving that legitimacy by careful explanation of the legal basis for their decisions.  This seems particularly true when invoking equity.

[1] Equity in International Law, American Society of International Law Proceedings, April 20-23, 1988,published in 82 Am. Soc'y Int'l L. Proc. 277.

ASIl & International Judicial AcademyInternational Judicial Monitor
© 2015 – The International Judicial Academy
with assistance from the American Society of International Law.

Editor: James G. Apple.
IJM welcomes comments, suggestions, and submissions.
Please contact the IJM editor at