The Binding Force of International Law

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by Patrick M. Capps

I. Introduction

It is commonly understood that international law is, at least in part, a set of binding legal norms that regulate the relations between states. Inquiry into the notion of the binding force of international law is an examination of the reasons why states are commanded, permitted or prohibited from undertaking certain actions and how states acquire certain rights, duties, powers or immunities against other states. A starting point for considering the binding force of international law is the famous decision of the Permanent Court of International Justice on the 7 September 1927 which concerned a dispute between France and Turkey over a collision between the French steamer, the Lotus, and a Turkish collier. In its judgment, the Court set out that the binding force of international law arose from the actual or tacit consent of states. Consent, in other words, is a law-creating fact. World public order is, then, a complex web of bilateral and multilateral agreements between states alongside a body of customary norms.

The position in the Lotus Case is both widely accepted and highly controversial. In 1928 Brierly said that this decision was ‘based on the highly contentious metaphysical proposition of the extreme positivist school that the law emanates from the free will of sovereign independent States.’ (BRIERLY, 1928: 155) Elsewhere he explains why he thinks it is contentious. He says ‘consent cannot of itself create an obligation; it can do so only within a system of law which declares that consent duly given, as in a treaty or a contract, shall be binding on the party consenting.’ (BRIERLY, 1950: 54) Therefore, there is a theoretical hole in this positivist concept of obligation despite its simplicity, popularity and intuitive plausibility. It cannot explain why international law is binding as law.

An explanation must be found to show how Brierly’s ‘system of law’, whereby state consent becomes a law creating fact, arises. It is this explanation, rather than the superstructure of agreements and customs which form substantive international law, which forms the basis of a world public order. There are at least two types of answer to this problem. One denies that these fundamental norms exist at the heart of an autonomous legal order and, for this reason, international legal obligations do not exist. Norms which regulate inter-state relations are, therefore, better construed as norms of prudence, morality or rules-of-thumb. A second accepts that there is an autonomous international legal order which is based on fundamental natural or conventional rules from which binding international legal obligations arise.

II. Deniers of the Binding Force of International Law

The first argument rests upon the premise or argument that sovereign states are the highest source of legal authority. If such states were subject to international legal obligations which, for example, regulated the jurisdictional scope of their laws it would mean that they were not the highest source of legal authority and hence could not, by definition, be sovereign. This, then, sets up the choice between a world of sovereign states, or a global state governed by international law. There is no third alternative and the global state is theoretically, normatively or practically unacceptable. Therefore, international law and international legal obligation cannot, genuinely, exist.

A. Thomas Hobbes (1588-1679)

One version of this argument is offered by the English philosopher Thomas Hobbes. Hobbes argued that legal obligations can only arise from the will of a sovereign legislator. Human beings agree to this way of governing their lives primarily because of the unreasonableness of the state of chaos and disorder which exists without the sovereign. He then argues that this logic does not imply a universal state to regulate a prima facie similar situation in international relations. One reason for this is that sovereign states do not have the same vulnerabilities as human beings (in that they don’t sleep or grow frail with age) and another is that an inter-state system does provide some degree of security for individual human beings. Therefore, some of the premises which propel Hobbes’s argument for the sovereign state do not apply to the relations between states (HARRISON, 2003: 96). Hobbes, then, considers a global or universal state logically unnecessary.

Hobbes does not think that international relations is completely devoid of rule-based activity. He argues that a very thin conception of society exists in international relations in which states tend to act in predictable ways. This is the case because states self-interested calculations imply that, most of the time, they do not act in an aggressive manner toward each other and they tend to keep their promises. However, these rules are not legally binding because law cannot exist without a sovereign legislator and there is no logical reason for having such a power to regulate international relations. Hobbes’ idea that self-interest produces a tendency towards stability and order in an anarchical order is one that has come to lie at the heart of approaches to international relations which are based upon game theory (HOLLIS AND SMITH, 1989: Chapters 6 and 8).

B. John Austin (1790-1859)

Albeit on the basis of an analytical or empirical rather than normative methodology, John Austin offers a similar argument to that of Hobbes. Austin claims that the sovereign as the source and enforcer of law is an essential component of legal order. While it is the case that the sovereign is present in all stable domestic legal orders, it is absent from international law. For this reason, he thinks that international law is better conceptualised as positive morality. International laws, therefore, are better understood as a set of posited rules but which do not carry genuine legal obligations.

C. Georg Jellinek (1851-1911)

Another final example of this type of account of the binding force of international law, which steers between normative and empirical methodologies, is provided by Georg Jellinek in his ‘two-sides’ theory. The juridical side leads to the conclusion that the sovereign state cannot be subject to a higher law such as international law, but rather is constituted as a ‘will’ that can bind itself. The problem identified by critics of Jellinek was that such an obligation vanishes once the state changes its mind. It might, then, be questioned whether an obligation which need not be complied with really is an obligation. But this mistakes two core elements of Jellinek’s approach.

Firstly, the sociological or psychological, side to Jellinek’s theory takes into account ‘the structural constraints imposed on State will by the environment.’ (KOSKENNIEMI, 2002: 201) This is much the same as Hobbes’s explanation of why states tend to act in certain ways in international relations. Secondly, domestic public and administrative law in general is, in effect, an exercise in self-legislation and this is not thought to imply a set of contingent norms which can be violated by the state at will. So why should it then be presumed that international law is any different to state public law when it comes to the binding effect of self-legislation? This ingenious argument for self-legislation does preclude the possibility of an autonomous international legal order existing or genuine international legal obligations arising. It does not, however, preclude the possibility that international laws are intrinsically incapable of having a legally binding effect. On this account, it is appropriate to say that the formal source of the international law – that is, why it is valid – is the same as any other public law of the state legal order. However, the material source of international law – which ‘denotes the provenance of the substantive content of that rule’ (JENNINGS AND WATTS, 1996: 23) – is to be found in treaties, declarations, and so on, derived from the mutual consent of states.

On this account, international law is, at best, understood as external state law or as a set of structural constraints placed on states by the warp and weft of international relations. Hans Kelsen (1881-1973) severely criticises this approach to international law. He considers that ‘[s]uch a justification is based on a fallacy, involving in a disastrous way the ambiguity of the concept of sovereignty - meaning the highest legal authority and unlimited freedom of action. This fallacy, however, is a permanent part of the political ideology of imperialism, with its operative dogma of state sovereignty.’ (KELSEN, 1998: 536)

III. Explanations of the Binding Force of International Law

The second approach to solving the problem identified by Brierly is to claim that states are constrained by an autonomous international legal order based upon a set of rational or conventional norms which afford legal validity to the system and render its norms legally binding.

A. Hugo Grotius (1583-1645)

The second approach approximates to the approach taken by Hugo Grotius in his foundational work on international law entitled De jure belli et pacis (1625). He claims that there are certain laws which must be the case ‘if people have a basic right not to be harmed in their lives, bodies and possessions [and] … a right to have their agreements kept.’ (HARRISON, 2003: 145) He furthermore argued that these laws could be unilaterally enforced by individuals, but that it was ‘much more conductive to the peace of individuals’ (GROTIUS, 1925: 91) that they submitted their wills to a sovereign state to operate as the arbiter and enforcer of these natural rights. However, the international legal order, he argued, was a set of natural laws which regulated the use of force by, and agreements between, states. These formed a body of norms called international law which were rationally binding and which could be unilaterally enforced by states. This is, then, a decentralised view of international legal order as opposed to the centralised conception of law associated with the modern state.

B. Immanuel Kant (1724-1804)

Immanuel Kant thought that such rational natural laws provided the logical impetus to a form of cosmopolitan international order. Kant’s views on what this might mean remains unclear. At some points, he comes close to the Grotian view of international law by arguing against a global state and for a horizontal and diffuse form of international legal order. At others, he seems to advocate a more substantial form of global governance. This comprises of three interlocking forms of juridical constitution which regulate different spheres of human activity. These are (i) nation states; (ii) public international law; (iii) ‘the constitution conforming to the law of world citizenship’ (KANT, 1957: 10-11, note 1).

The seminal Kantian constructivist, John Rawls (1921-2002), takes the first of Kant’s lines in his recent work on global justice by arguing that the global state is both unjust and impractical (RAWLS, 1999: 36). He does not, however, explore in detail the institutional ramifications of taking this line, or, indeed explain how international laws come about and why they become binding. He does, however, give strong grounds for underlying moral principles which must rationally govern international relations and this constitutes a substantial theoretical advance which can be built upon by international lawyers in the future.

C. Herbert Hart (1907-1992)

A legal positivist like Herbert Hart would consider that there is a different explanation for the development of the basic rules which validate Grotius’ horizontal system. For Hart the validity of a legal system is determined by a rule of recognition. Presumably, in an international legal order, this rule of recognition allows legal officials in various states to discern their international legal obligations from other sorts of obligation (for example, the rules of etiquette regulating diplomatic visits). Although Hart is sceptical as to whether a rule of recognition exists in the international legal order, if it does, it comes into being because it is practised by legal officials and it is binding for this reason.[1] So the Grotian idea that there are natural laws discerned from reason are replaced in Hart’s account by conventional rules which have developed over (perhaps) hundreds of years.

D. Hedley Bull (1933-1985)

Modern Grotians like Hedley Bull explain the binding force of international law by combining a natural law and conventional account. Bull considers that there are certain norms which are accepted by states as being necessary for social life to occur in international relations. These are an ‘empirical equivalent’ of natural law (BULL, 1977: 6). These rules require the preservation of the international society of states, the maintenance of the independence of states as well as providing a limit on violence and the stabilisation of property rights. This seems similar to the Grotian account. However, Bull then argues that this has to ‘be set against the cultural and historical forces that had helped shape the consciousness of society at any particular time and moulded perceptions of common values and common purpose.’ (BULL, 1977: xi) Therefore, the reasons why obligations arise are rooted in reason, but over time common values develop which help to generate a thicker conception of those norms which are obligatory in international law.

IV. Theoretical Problems with the Consent-based Account of Obligation

Two connected points need to be made about these various accounts of the binding force of international law. The first is to notice that there is little disagreement on the substantive norms which constitute international law. Restrictions on the use of force, the independence of states and pacta sunt servanda are uncontroversial norms which guide action in international relations. The differences between the accounts just considered surround the reasons why these substantive norms are binding on states. Those who deny that international law can be legally binding would consider these rules to be good rules-of-thumb or as rational actions given that states are self-interested or morally motivated. The other accounts consider these substantive rules as norms derived from further foundational norms all of which form part of an autonomous legal order. Of course, all of this depends upon the necessary and sufficient conditions for a norm-system to be designated as legal.

Kelsen’s very controversial response to this distinction is that it collapses; both approaches map equally well on the corpus of positive norms which are normally called international law. Legal scientists can disagree on the question of why international law is valid but the substantive content of international law remains the same from either perspective. He claims ‘[b]oth frames of reference are equally correct and equally warranted. It is impossible to choose between them on the basis of legal science.’ (KELSEN, 1998: 535) One might be sceptical about the conceptual validity of this claim. This is because the coincidence that Kelsen points out may turn on the contingent empirical fact that it is normally states, through their consent, which make international law. Also, Kelsen’s approach moves the question of the bindingness of international law beyond the purview of legal science. John Finnis may be right when he suggests that much of Kelsen’s approach rests upon ‘an overtly fictitious construction designed to suppress theoretical questions rather than to answer them.’ (FINNIS, 1973: 67)

Secondly, this inquiry into the binding nature of international law has been restricted to considerations of how state consent becomes a law-creating fact. This appears to presuppose that international law is a decentralised or horizontal order of norms. As we have seen, some have been inspired by this observation to conclude that the rules which govern international relations are not legally binding. But this is the case if international legal order can only exist in the modern, centralised and bureaucratic form with which we are familiar. Against this, it should be realised that the modern state system emerged from the very different imperium mundi which was the Holy Roman Empire. This shows that while the horizontal inter-state system is old and familiar it is also contingent. If the inter-state system is replaced by a return to earlier ideas of political and legal order, a system of international law distinct from the decentralised model presupposed in the Lotus decision may arise. Whether such an order will be legitimate, effective or stable is another matter.

The Grotian approach is an intermediary between this ‘all-or-nothing’ approach to questions of the bindingness of international law. So, while Hobbes thinks that there is no room for international law between the rules of thumb which develop in an anarchical international society and genuine legally binding norms promulgated by a global sovereign state, Grotians claim that laws can be binding qua law in the absence of a sovereign legislator. This approach can then justify a decentralised, diffuse but legally binding system of international law. This said, there are several problems with this approach. One is that it not particularly effective at achieving certain global ends (for example, distributive justice) because it is a mainly permissive order. A second is that its rules are often vague, contradictory or unclear simply because they are not legislated for. This criticism would be that such a system does not serve to effectively stabilise the expectations a state may have in international relations. Even more problematically, it permits states, in some circumstances, to unilaterally enforce breaches of international law (e.g. self-defence) and this is often not conducive to peace in the long-term. It is, on the other hand, a system which has allowed co-operation and co-existence to occur over a long period as well as being the framework within which a deep consensus has emerged as to the values which should be instantiated in international legal rules. It should therefore not be simply discounted as a system which is best characterised as a set of rules which are sometimes adhered to by states if it is in their interests to do so.


Brierly J., ‘The “Lotus” Case’ [1928] 174 Law Quarterly Review 154

**Brierly J., The Basis of Obligation in International Law (Clarendon Press, Oxford, 1958)

Brierly J., The Law of Nations (Oxford University Press, Oxford, 1950)

**Bull H., The Anarchical Society (Palgrave-MacMillan, Basingstoke, 1977)

Finnis J., ‘Revolutions and the Continuity of Law’ in A. Simpson (ed), Oxford Essays in Jurisprudence (Oxford University Press, Oxford, 1973)

**Grotius H., The Rights of War and Peace (Clarendon Press, Oxford, 1925, first published in 1625, translated by F. Kelsey)

Harrison R., Hobbes, Locke and Confusion’s Masterpiece (Cambridge University Press, Cambridge, 2003)

**Hart H., The Concept of Law (Clarendon Press, Oxford, 1961)

**Hollis M. and Smith S., Explaining and Understanding International Relations (Clarendon Press, Oxford, 1990)

Jennings R. and Watts A., Oppenheim’s International Law, 9th edition (Longman, London, 1996, first published in 1905)

**Kant I., Perpetual Peace, (MacMillan, New Jersey, 1957, first published in 1795, translated by L. Beck)

**Kelsen H., ‘Sovereignty’ in S. Paulson and B. Litschewski Paulson (eds), Normativity and Norms (Oxford University Press, Oxford, 1998)

Kelsen H., Introduction to the Problems of Legal Theory (Oxford University Press, Oxford, 2002, originally published in 1934)

Koskenniemi M., The Gentle Civilizer of Nations: The Rise and Fall of International Law 1870-1960 (Cambridge University Press, Cambridge, 2002)

Oppenheim L., “The Science of International Law: Its Task and Method” (1908) 2 American Journal of International Law 313

**Rawls J., The Law of Peoples (Harvard University Press, Cambridge, Mass., 1999)

Tuck R., The Rights of War and Peace (Oxford University Press, Oxford, 1999)

(** indicates recommended reading)

Related Entries

binding force of constitutional lawJohn AustinConventionGame theory in jurisprudenceHugo GrotiusHLA HartThomas Hobbesconcept of lawlegal positivismpure theory of law.


[1] In chapter 10 of The Concept of Law (Clarendon Press, Oxford, 1961), Hart denies that a rule of recognition exists in the relations between states and therefore it can be questioned whether an international legal order exists. He does, however, claim that ‘in this analogy of content, no other social rules are so close to municipal law as those of international law.’ (at 237) We might, however, conclude that Hart misinterpreted the sophistication of the regulatory framework existing in the relations between states at least since the advent of the United Nations system, and probably even before this development. On this point see Hart’s discussion on 257 concerning Article 38(1) of the Statute of the International Court of Justice in relation to the sources of international law.

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