Thursday, March 19, 2009

A relation between opinio iuris and state practice in making customary international law - part I

Custom is a form through which one of the traditional sources of international law is created. According to the common view of contemporary legal theory, international custom consist of two distinct elements: A practice of states (usus) and an assenting view of states, approving the practice in question as lawful (opinio juris) or necessary (opinio necessitatis). One has to explain how both of them can be understood in order to discuss a balance between these two elements.

We could say the state practice is simply everything that a state really is actually doing. This statement implies the question of how the acting of a state relates to law, in particular, to a body of rules which govern relations in international community. Generally, we can distinguish between behaviour which is regulated by law, qualified either as permitted or forbidden, and those which is not regulated. The latter would become essential for the evolution of a new customary international law, if it is not contradictory to economical, political or military interests of an overwhelming majority of other states. Further it has to be considered to be in accordance with ius de lege ferenda. State practice must last for certain time in certain quality. In theory, this is normally called an objective element. However, a subjective element must be present as well. It must be at least possible to deduce a normative element from the concerned behaviour. In contrast to opinio iuris, state practice contains an expression of will about a necessity of a new pattern of behaviour. Requirements for quality of state practice were clearly stated in a judgement of International Court of Justice (ICJ) in Nicaragua (merits): ‘In order to deduce the existence of customary rules, the Court deems it sufficient that the conduct of States should, in general, be consistent with such rules, and that instances of State conduct inconsistent with a given rule should generally have been treated as breaches of that rule, not as indications of the recognition of a new rule.’[1] Customary rules on exclusive exploitation of natural resources in high seas are a good example as it is based on state practice. In other areas, especially those connected with protection of human rights, the state practice is not so important, as is stated above in Nicaragua case concerning non-intervention and prohibition on use of force.

The second fundamental element is the conviction of state that one acts in accordance with existing international law or it suits common needs of the international community to behave in that way. Opinio juris is very often created by state practice under opinio necessitatis. A classic definition was made in the judgement of ICJ in North Sea Continental Shelf Case, stating ‘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 be evidence of a belief that this practice is rendered obligatory by the existence of a rule of law requiring it. The need for such a belief, i.e. the existence of a subjective element, is implicit in the very notion of the opinio juris sive necessitatis. The states concerned must therefore feel that they are conforming to what amounts to a legal obligation. The frequency or even habitual character of the acts is not in itself enough.’[2] In other words, to complete a creation of a new rule, opinio juris is a precondition. But there is no synchonicity of the two elements. Only one of these two have to appear earlier. Therefore, it is not necessary, so it seems, that both of the elements are present at the very beginning of an emergence of a new norm of customary international law. It does not matter which of the elements comes first, it has no impact on the very nature of the emerging rule. However, a balance between both of them is usually established in this way. A prohibition on reprisals against civilians serves as an example of rule under customary international law. There, opinio juris is the most important element, ‘even where State practice is scant or inconsistent’[3].

[1] International Court of Justice, Nicaragua (merits), at §186.
[2] International Court of Justice, North Sea Continental Shelf Cases, at §77.
[3] International Criminal Tribunal for the Former Yugoslavia, Zoran Kupreškić and others, at 527.

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