Opinio Juris as (the Ultimate) International Secondary Rule of Recognition: Reconciling State Consent and Public Conscience

Abstract

International secondary rules of recognition regarding international law-making are subject to the criticism that legal officials accepting them were confined to a limited number of public actors. Concerning customary international law, opinio juris can reflect not only the will of sovereign States but also the juridical conscience of various international social actors taking action on behalf of the public. Assuming such a coexistence of State consent and public conscience, this paper explores the uncharted aspect of opinio juris ‘systemique’, which has the potential to integrate the principles of pacta sunt servanda, on the one hand, and of voluntas civitatis maximae est servanda, on the other hand. The first part of the paper shows opinio juris exists in every formal source of international law, as acceptance of international custom, consensus of treaty interpretation and recognition of general principles of law. This analysis simultaneously unlocks the possibility of juxtaposing public conscience with State consent. The second part adapts the rule of recognition theory to opinio juris which is equipped with public conscience as well as State consent. By additionally incorporating the aspect of public conscience beyond State consent into opinio juris, this paper aims at moralising this rule of recognition to include both social facts and substantive values as the decisive factors of the validity of international law; at relativizing it to modify the absolute position which dichotomises the normativity of international law; and finally, at democratising it to reduce the prominence of the voluntarist legitimacy of international law.