A common law of the world? The reception of customary international law in the Canadian common law.

AuthorLeBel, Louis
PositionThe Impact of International Law on Canadian Law


In an increasingly globalized world, the importance of international law to our domestic legal system continues to grow. This growth is both exponential and multidimensional. International law had been traditionally concerned with relations between states and about the status and action of international organizations. But today, not only is international law having a greater impact than ever on the state of domestic law, it also influences more areas of domestic law than ever. These areas include human rights, labour law, commercial law, intellectual property law, immigration and refugee law, and criminal law, to name but a few.

In this paper, I intend to focus on the means by which customary international law exerts its influence on the Canadian domestic legal culture. As will be discussed in greater detail below, customary international law is developed by state practice and the recognition of the legally binding nature of this practice, while other parts of international law are grounded in treaties and other multilateral instruments, which reflect the contractual activities of states and organizations. I will address some intricacies of this process. Before I do so, however, I will use again an analogy which, at least for the classical music lovers, may be of some assistance to understand the issues of interaction of international and domestic law.

A number of years ago, I co-wrote an article describing how the reception of international law into the Canadian legal order could be usefully compared to two distinct classical musical styles. First, there is the "fugue" style, from the Baroque period, in which "one or two themes are repeated or imitated by successively entering and interweaving repetitive elements." (1) The second style is "fusion"--"a merging of diverse, distinct, or separate elements into a unified whole," or "the combination of different styles ... to form a new style." (2)

Metaphorically, these two styles refer to two different approaches to the internalization of international law. Under the fugue approach, the domestic and international legal orders operate independently, and are only interwoven when international law is formally incorporated, or "transformed", into the domestic order. This method may also be termed the dualist approach to reception, under which international law must be expressly received to by some executive and/or legislative action in order for it to be effective domestically.

In contrast stands the fusion approach, which is synonymous with the monist approach to reception. Under this approach, international law is directly incorporated into domestic law and is immediately effective without any additional legislative or executive action. Just like the music created by this style, the fusion approach modifies the domestic law and changes it from what it might otherwise have been.

Subject to certain exceptions, upon which I will elaborate, the Canadian approach to the reception of customary international law has moved decidedly towards the "fusion" end of the spectrum. By and large, customary international law is now directly incorporated into the common law of Canada and is effective immediately without the need for further legislative or executive action. I will first discuss what constitutes custom in international law and how it develops. I will then review the development of the law regarding reception of custom into the domestic legal order, in the U.K. and in Canada. Finally, I will turn to some specific problems and issues raised by the Canadian approach to the reception of customary international law.


A logical starting point is to describe, briefly, what customary international law is and how it gets recognized. Article 38(1) of the Statute of the International Court of Justice identifies the various sources of international law, as follows:

(a) international conventions, whether general or particular, establishing rules expressly recognized by the contesting states;

(b) international custom, as evidence of a general practice accepted as law;

(c) the general principles of law recognized by civilized nations;

(d) subject to the provisions of Article 59, judicial decisions and the teachings of the most highly qualified publicists of the various nations, as subsidiary means for the determination of rules of law.

My comments focus on the second category--international custom, as evidence of a general practice accepted as law. What the inclusion of this category in the Statute of the International Court of Justice confirms is that, at its most basic level, customary international law is a source of law. In other words, it is a source of legal obligations binding on all states. This rule is subject only to one controversial exception, known as the "persistent objector rule." This rule holds that a state which has persistently objected to a particular rule of customary international law, during its formation and since its inception, will not be bound by that custom. (3) But, this begs the question of what turns a given principle or rule into an international custom and binding law?

  1. Recognition of Custom

    Customary international law is developed by generalized, though not necessarily universal, state practice. Specifically, two requirements must be met in order for a particular rule or principle to be considered an international custom. First, the principle or rule must be generally observed or accepted as a state practice. To determine whether this is so, one enquires as to whether the majority of states are adhering to the rule or principle in their physical acts, claims, declarations, laws, and judgments. The rule must be recognized as a state practice by most, but not all nations. As the Supreme Court of Canada held in the Continental Shelf Reference, "[i]n order to constitute a custom there must be substantial uniformity or consistency, and general acceptance". (4) Clearly, the use of such adjectives as "substantial" and "general" confirm the recognition of a custom does depend on the generality of a practice, but not on its absolute universality.

    The second requirement is that states follow the principle or rule out of a sense of legal obligation, not simply out of courtesy or morality. This is known as opinio juris, as the International Court of Justice held in the North Sea Continental Shelf case in this way, "Not only must the acts concerned amount to a settled practice, but they must also be such, or be carried out in such a way, as to constitute evidence of a belief by the state parties that a practice is rendered obligatory by the existence of a rule of law requiring it." (5)

  2. Regional Customs

    Before turning to the reception of customary international law in Canada, I must add a precision to the definition of custom and, in particular, to the notion that customs are a source of binding legal obligations on all states. Certain customs, instead of being general in nature, may be practised only within a particular region. This may lead to the development of a local customary law which is binding only on those states within the region. In fact, as few as two countries may establish a binding local custom as between themselves. (6) Importantly, regional customs are created in the same way as general customs. That is, the alleged custom must be established by state practice in the region to which it appertains and there must be opinio juris amongst the states who are alleged to be bound by it.

    Against this background, I will now discuss the reception of customary international law into the Canadian common law. Our system of reception is rooted in the British tradition, which will provide a useful starting point for my analysis.


  3. Historical Controversy and the British Approach

    As early as 1737, it was seen as settled law in England that customary international law was automatically or directly incorporated as part of that country's common law. (7) This remained so until 1876, when the case of R v Keyn (The Franconia) (8) put this assumption in doubt. In this judgment, Chief Justice Cockbum, adopting a firmly dualist approach, held that, for England to be bound by an international rule or a principle of international law, an Act of Parliament was necessary. Of like effect, although somewhat equivocal, was the Privy Council's 1938 decision in Chung Chi Cheung v The King. (9) In that case, Lord Atkin emphasized the need for a process of incorporation of rules of international law into the domestic law of the United Kingdom:

    ... international law has no validity save in so far as its principles are accepted and adopted by our own domestic law. There is no external power that imposes its rules upon our own code of substantive law or procedure. The Courts acknowledge the existence of a body of rules which nations accept amongst themselves. On any judicial issue they seek to ascertain what the relevant rule is, and, having found it, they will treat it as incorporated in to the domestic law, so far as it is not inconsistent with rules enacted by statutes or finally declared by their tribunals. (10) Whether these cases, in fact, constituted a complete rejection of the doctrine of direct incorporation remained uncertain. For example, the Keyn decision was followed by a decision approving of the doctrine of direct incorporation of customary international law. (11) Even, the dicta from Chung might be viewed as largely consistent with the doctrine. Indeed, the only portion of the above quoted excerpt from Chung which appears inconsistent with the incorporation doctrine, as it is understood today, is Lord Atkin's position that the reception of customary international law may be barred by existing conflicting common law. But, as an author observed, at the time Chung was decided, the issue of conflict between a norm of customary international law and the existing common law had not been considered...

To continue reading

Request your trial

VLEX uses login cookies to provide you with a better browsing experience. If you click on 'Accept' or continue browsing this site we consider that you accept our cookie policy. ACCEPT