Louis Henkin popularly remarked that “[it] is probably the case that almost all nations observe almost all principles of international law and almost all of their obligations all of the time.” The obvious question that arises concerns the veracity or otherwise of this statement. As Harold Koh identifies, the question why nations obey international law remains one of the most perplexing and fundamental questions in international relations, both from practical and theoretical points of view.

Granted that international law rules are truly obeyed by states, the enquiry brings us to an even higher and more perplexing jurisprudential question of what international law is and whether international law is truly law. Whereas the second part of the enquiry about whether international law is truly law is beyond the scope of this paper, the first part will be dealt with, albeit briefly.

Interestingly, there is no universally accepted definition for international law. Now this should not surprise any student of international law because even ‘law’ itself has no definition. Nonetheless, some working definitions have been provided for international law. The authorities are congruent that the term “international law” was first used by Jeremy Bentham in his Introduction to the Principles of Morals and Legislation, which terminology came later to replace the older term “law of nations.” In an attempt to define international law, authors and jurists have largely been persuaded by what they construe to be the subjects of international law in the formulation of definitions for the concept.

Accordingly, Peter Akehurst notes that until the inter-war period, “writers found no difficulty in defining (public) international law, in one formulation or another, as the law that governs the relations between states amongst each other.” This is because the prevailing positivist doctrine at the time regarded only states as subjects of international law, although Peter Akehurst questions the propriety of this view, since the Holy See which was not a state was recognized as an international legal person.

From the period of the European tribal wars which have succeeded in being described as “world wars”, a number of international actors started emerging, thus necessitating a changing notion of international law.  Due to this, attempts were made to redefine international law to encapsulate the changing trend in the admission of many candidates of international legal personality.

For instance, the Restatement (Third) by the American Law Institute of the Foreign Relations Law of the United States defines international law as consisting “of rules and principles of general application dealing with the conduct of states and of international organizations and with their relations inter se, as well as with some of their relations with persons, whether natural or juridical.”

Through the vicissitudes of time, the veracity of the felicitous language of the draftsman in the aforementioned definition is doubtful. It does not quite reflect the reality in the twenty first century since there are many other international legal persons, aside states and international organizations. In view of this, and in order not to provide a working definition for international law that will fail to encapsulate all of the actors in the international plane now or in the near future, I would conveniently define international law in the following terms. International law can be said to be the set of rules and principles that govern the relationship that exists between and among the various subjects of international law on the one hand and the interactions of each of them with other persons, natural or artificial, on the other.

Moving on to why states obey international law rules, an enquiry into the archives of history reveals that during the formative years of international law, instead of providing answers to the question why states obey international law rules, writers rather answered a similar but materially different question of why they should obey. In so doing, the authors justified their answers as to why they should obey by advancing arguments that were more theistic than legal, by making reference to a higher law – the law of nature, of which international law was but a microscopic fraction.

Historically, in response to the question why states obey international law, there were those practitioners in a school of thought largely regarded as the Austinian positivistic realist strand of thought spearheaded by John Austin. They argued that international law was never truly obeyed because it is not really law.

There also emerged the Hobbesian utilitarian rationalistic school of thought, the key proponent of which was Thomas Hobbes. Students of this school argued that nations sometimes follow international law. However, they do so only when it serves their self-interest.

The third line of thought that emerged was that which was advocated by Immanuel Kant and like-minded individuals. This doctrine posited that nations obey international law guided by a sense of moral and ethical obligation derived from considerations of natural law and justice. Kant viewed international law as a purposive system dedicated towards securing peace and built on the cornerstones of justice, democracy and liberalism focused on the centrality of human rights. In his work To Perpetual Peace, Kant specifically urged states to take cues from philosophers and follow international law not as an end in itself but as a route toward an end, which is “perpetual peace”.

Again, there arose the Benthamite argument which suggested a possible ground for obedience. Bentham argued that a nation’s incentive to obey is derived from the encouragement and prodding of other nations with whom it is engaged in a discursive legal process.

Apart altogether from the already identified, James Leslie Brierly identifies two rival traditional justifications for obeying international legal rules. He identified the doctrine of the natural or fundamental rights of states as well as the doctrine of consent.

The supporters of the doctrine of the fundamental rights of states argued that this doctrine is a necessary corollary of the doctrine of the state of nature in which men were supposed to have lived before they formed themselves into political communities or states. Now, states having formed themselves into a superstate are still supposed to adhere to this doctrine by living in such a condition. This therefore requires of states to obey international legal rules just as humans were to obey national laws.

The doctrine of consent as identified by Brierly posits that international law is the sum of rules by which states have consented to be bound, and nothing can be law to which they have not consented. This consent, according to those who subscribe to this view, may be given expressly in the case of a treaty or impliedly by acquiescence to a customary rule. Having expressed themselves to be bound by these rules, therefore, common sense requires of states to obey these rules which they have themselves created or consented to.

However, Brierly contends that the assumption that international law consists of nothing save what states have consented is an inadequate account of the system as it can be seen in operation. He argues further that even if it is a complete account of the contents of the law it would fail to explain why the law is binding. Also, he expressed the view that the doctrine of implied consent of states is not a philosophically sound explanation of customary law, domestic or international. Therefore, a customary rule is observed not because it has been consented to but because it is believed to be binding and whatever the justification for that belief, its binding force does not depend, and is not felt by those who follow it to depend, on the approval of the individual or the state to which it is addressed.

Alfred Verdross founded the pivotal cause of compliance on what is popularly regarded as the Grotian commonality of interests and values which drives states to honour agreements they enter into. As such, states obey international law because they have a common beneficial interest, which can be attained by obedience to international legal rules. Perhaps building on this, Brierly refused to predicate reliance on either natural law or positivist consent as sources of legal obligation. He therefore suggested the need to preserve solidarity with one’s fellow states as the reason for compliance.

Some authors have also argued that the declaration of friendly relations (consensus) between nations is what accounts for compliance. For instance, Malcolm Shaw indicates that states do not restrict their behavior to what is legally required but rather pursue a line of conduct purely through a feeling of goodwill and in the hope of reciprocal benefits.

Abraham Chayes and Antonia Chayes take the firm stance that nations are pulled towards compliance not for fear of sanctions but because of the dynamics created by the treaty regimes to which they are part. This view appears to reiterate the argument on the basis of consent that nations obey international law rules because they have consented to those rules through treaties which have imposed upon them the obligation of compliance. In sharp contrast, Prof. Thomas Franck argues that the key to compliance lies largely in the fairness of international rules themselves. As such, nations obey “powerless rules” because of considerations of legitimacy (right process) and distributive justice. In Franck’s view, anything short of this would usually not be complied with by states.

These two opposing arguments by the Chayeses and Franck have been objected to by Harold Koh who posits rather that these two arguments fail to address “a thoroughgoing account of transnational legal process: the complex process of institutional interaction whereby global norms are not just debated and interpreted, but ultimately internalized by domestic legal systems.” He adds that they fail “to describe the pathways whereby a “managerial” discourse or “fair” international rule penetrates into a domestic legal system, thus becoming part of that nation’s internal value set.” He therefore concludes that “this overlooked process of interaction, interpretation, and internalization of international norms into domestic legal systems is pivotal to understanding why nations “obey” international law, rather than merely conform their behavior to it when convenient.”

To some extent, I disagree with the postulation by Harold Koh in the sense that he appears to have misapprehended what the whole idea of compliance entails. This is because his consideration of compliance is conflated with the issue of implementation, whereas the two relate to different things altogether. As Prof. Harold K. Jacobson and Prof. Edith Brown Weiss identify, implementation has to do with the means by which international legal norms are transformed into domestic legal rules, thereby forming a part of the legal system of the state concerned. On the other hand, compliance has to do primarily with whether states do abide by the terms of international legal norms.

Accordingly, whereas states may obey international legal norms that are incorporated into their system, it does not remove possibilities of obedience to international laws which may not yet be domesticated. Again, states may obey international legal rules, although they have not been incorporated into the domestic legal system.

Put differently, Article 75(2) of the 1992 Constitution of Ghana for instance requires that treaties entered into by the Executive be ratified by Parliament through at least one of two means provided thereunder: ratification by an Act of Parliament or a resolution supported by more than half of all members of Parliament. However, under international law as encapsulated in Article 27 of the Vienna Convention on the Law of Treaties (VCLT), a state party to a treaty “may not invoke the provisions of its internal law as justification for its failure to perform a treaty.” This means that as far as international law is concerned, compliance and internalization of international legal obligations are poles apart. Whereas the latter may sometimes lead to the former, it is not always the case that internalized laws will be complied with. Conversely, there are also instances where international legal rules are complied with, although they have not gained the effect of law in the domestic legal system.

Moving on, if one were to consider the compliance question critically, it would appear that whereas a variety of factors may account for compliance with international law principles, there is one compelling reason that can be said to be the crème de la crème of compliance with international law rules. To wit, I refer here to the factor of the self-interest of the state.

In any real sense, a nation would abide by international law rules because of its self interest. This can manifest itself in a number of forms. It can be as a result of the fact that the consequences of non-compliance will be disastrous to the nation in question or rather that performance of the international legal obligation confers a benefit on the nation. In other words, considering the proposed grounds for compliance identified above, if one examines them to their full effect, it will be revealed that those grounds would be rooted in the conferment of some benefit on the state or the avoidance of something that will be adverse to the interest of a state.

For instance, if fear of sanctions motivates a state to comply with its international obligations, it is because the sanctions that may result from non-compliance may be perilous to the nation. Similarly, obeying international legal obligations for purposes of reciprocal benefits translates into the self-interest of the state, since the reciprocal benefits will be a matter of great interest to the state. Again, a state may obey international law rule by reason of the fact that it has expressed itself to be bound by it. And ordinarily, a state will not consent to be bound by any rule that does not confer a benefit on it. Even if it does not confer a benefit on the state, at least it must not be adverse to the state’s interest. That is the point where the self-interest of a state becomes the principal factor that determines whether or not a state would obey international law rules.

Inevitably, another compelling reason that will push one to believe that the self-interest of states is the overriding factor that determines their compliance can be gleaned from the attitude of powerful nations like the United States of America. Arguably, no powerful nation will obey any international law rule whatsoever in so far as it does not confer any benefit on it, directly or indirectly. In fact, practice in the field of compliance alludes to this reality.

In conclusion, it is imperative to note that there may be numerous factors that account for a state’s compliance with international law rules. Nevertheless, when the compliance question is looked at objectively, all the enumerated grounds for compliance lead inexorably to one end. This end is the advancement of the self-interest of the state in question or, at the very least, the avoidance of anything that will be catastrophic to the nation’s interest as already shown in sparing detail above.