Is International Law really law or not?

What is “law”? Must it be rules written down? Can it be general principles? What about case law? Must “law” be enforceable? It seems that to say international law is not really law is too simplistic a view to take. There is no specific full list of what exactly is constituted within international law, and states can and do breach international law, but this is not to say that it is not an effective process, even if it may not be as black and white, or obviously “law”, as the domestic laws of individual states. 

The International Court of Justice considers a number of “sources” of international law when deciding a case, as listed in Article 38 of its statute: Conventions (i.e. treaties), Custom, General principles, Judicial decisions, Academic writing. This is not a complete list of the sources of international law as Article 38 is simply a direction to the International Court of Justice(ICJ), which does not in itself represent the totality of international law, and is not meant to exclude other matters that may be said to give rise to international rights (e.g. binding resolutions of other international bodies). Also, Article 38 provides no priority or hierarchy of the sources of international law, which can raise difficulties when different sources are conflicting. Dixonargues that the better view is that the priority of the sources follows the order in which they are listed in the Article. In practice, a treaty provision is applied over a rule of customary international law, in the event of inconsistency between them. That is, states can derogate from custom by way of treaty. Custom, in turn, is applied over a general principle of law, in the event of inconsistency. This practical hierarchy merely reflects the logic that the special rule (lex specialis) trumps the general rule (lex generalis) in the event and to the extent of inconsistency between them. There are three law-creating processes: treaties, international customary law and the general principles of law recognised by civilised nations.

To look firstly at treaties. Fitzmaurice has noted that treaties are a source of obligation rather than law. In this sense, they are no more a source of law than an ordinary private law contract, which simply creates rights and obligations, not law. A treaty may reflect, or lead to, law but in its inception it is not ‘law.’ Thus, there is really no such thing as ‘particular’ international treaty law, and the only ‘law’ that enters into these obligations is derived not from the treaty creating them but from the general principle ‘pacta sunt servanda’, which states that the obligation must be carried out, but is not, in itself, law. A treaty may codify existing law but this does not make it formally a source of law, just evidence of it. Treaties are voluntary in the sense that no state can be bound by a treaty without having given its consent to be so bound. As such, treaties bind only the parties to them. In contrast, customary international law is binding on all states. However, a treaty can become a material source of law, because the rules it contains come to be generally regarded as representing rules of universal applicability.

Customary international law is created by opinio juris i.e. a state’s belief that certain behaviour is required by law (as seen in North Sea Continental Shelf Case2), coupled with practice i.e. any act or statement by a State from which views about customary law can be inferred, including physical acts, claims, declarations, national judgments and treaty ratifications (Anglo-Norwegian Fisheries Case3). Akehurstargues that “as regards the quantity of practice needed to create a customary rule, the number of States participating is more important than the frequency or duration of the practice.” As such, major inconsistencies in State practice prevent the creation of a customary rule.

However, the paradox here arising is that customary law only develops through prima facie illegal conduct i.e. by a state no longer following the particular practice which gave rise to the custom, and in so doing the states must erroneously think that what they are doing is correct and legal5.

One must note that resolutions of the UN General Assembly are not themselves formal sources of international law, though they are useful material sources. A state’s vote in relation to a UN General Assembly resolution can be taken as both state practice and as opinio juris (Nicaragua6). In addition, obligations imposed via article 25 of the UN Charter are not a formal source of international law in their own right, but merely actualize obligations deriving from treaty.

As a result, one cannot simply say that “international law is not law.” The many factors detailed above that together constitute what is known as international law have formed what can only be described as a system as effective as many domestic legal systems. The lack of a specific code or constitution detailing exactly what constitutes “international law” is no different than the situation in many legal systems such as the UK! Thus, international law most certainly does constitute law, depending on what one’s view of ‘law’ is.

International Law, 6th eds OUP 2007.

ICJ 1969.

1951 I.C.J. Rep. 116.

Akehurst Modern Introduction to International Law, 7th Eds 2002. 

D’Amato 79 Northwestern Law Review 1293 (1985).

1984 ICJ. 

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