L’enigma delle consuetudini particolari

The international courts confirm for a long time the existence of unwritten rules of a limited effectiveness rationae personarum, commonly referred as particular customs. More precisely, a rule of particular customary law - whether regional, local or other - appears as a rule of customary international law that applies only among a limited number of States forming a group, in contrast to rules of customary law of general application. Since the 1950s Asylum case, the International Court of Justice considers the particular custom as a sub-system of the general one, following the same two-element approach and so requiring both a general practice and its acceptance as law (opinio juris). In the Court’s view, however, only those States which have accepted a particular custom are required to respect it. Indeed in this case, it is very difficult to distinguish between a mere psychological situation of opinio iuris and a contractual consent. In this way opinio iuris seems to bring about a real “tacit agreement”, leading into the realm of the pacta sunt servanda principle. All this has raised many doubts in doctrine which follows very different and contrasting approaches. But there is nothing to prevent the idea of the existence of a real “special custom” rationae personarum next to the particular custom thus undertstood, that all States belonging to a limited group have to observe it regardless of their adhesion or tacit consent, also in the case of a “persistent objector”. The international courts should admit this kind of norms - subspecies of general custom - as the general theory of law would require.