입법적 국제관습법과 법적확신 개념의 재구성

Article 38(1)(b) of the Statute of the International Court of Justice defines customary international law (CIL) as being “international custom, as evidence of a general practice accepted as law.” It has been generally understood that CIL is constituted, or rather, is ascertained to have been constituted, when the two elements of ‘state practice’ and ‘opinio juris’ are met. The discussions on the definition and elements of CIL has centered around the question of why and how adjudicators have confirmed the existence and content of CIL, rather than how CIL has actually been formed. Although the two-element scheme of CIL has been widely accepted on the basis of scholarly discourse and state practices, it always carries an air of ambiguity due to the unsettled and wayward manner of proving the two elements, and those theoretical difficulties such as the ‘chronological paradox.’ The subjective element of CIL—i.e., opinio juris—is an awareness of a binding nature of a certain state practice, and basically indicates a sense of obligation or cognition of obligation. At this juncture, a sense of obligation could be either of a legal or non-legal nature, e.g., stemming from ethics or other non-legal values. If opinio juris is defined on the basis of the notion of a legal obligation, it follows that a legal obligation already exists in advance of the establishment of a corresponding law—i.e., CIL. Thus, we are to stuck with a circular reasoning of ‘chronological paradox.’ On the other hand, if the concept of opinio juris encompasses both notions of legal obligations and non-legal obligations as was the case in the original latin term of opinio juris—i.e., opinio juris sive necessitatis, we could evade the fallacy of ‘chronological paradox.’ Customary law, essentially reflecting a community’s way of life formed for a long period of time, should inevitably be of a conservative and backward-looking nature. This aspect of customary law necessarily renders it unfit to adapt itself to a continuously changing society. On the other hand, CIL’s fundamental ambiguity vis-á-vis both the timing of its formation and its legislators provides adjudicators with a power similar to that of legislators in domestic legal systems. This unexpected law-making competence quietly vested in the adjudicators tends to render the process of identification of CIL a forward-looking exercise. In view of the current needs of international community and various reasons behind states’ acceptance of a certain state practice as legally binding, the concept of opinio juris should be reformulated as a flexible notion. This can be achieved by expanding the notion of opinio juris so that it could encompass not only the belief that a state practice is legally required but also the awareness that it is desirable now and in the near future to have a certain authoritative legal norm reflecting the social necessity of the international community.