Consent in international law can potentially have three different references: to specific outcomes or events (‘outcome consent’); to rules or norms (‘rule consent’); or to a legal regime as a whole (‘regime consent’). The effect of outcome consent is to convert something that is normally unlawful into something lawful. Rule consent and regime consent are sometimes difficult to distinguish from one another. Customary international law, most notably, can be seen from either perspective. From the standpoint of rule consent, customary law would be analogous to a treaty, in which active consent is given to rules on an ad hoc basis. From the standpoint of regime consent, customary law could entail, more broadly, consent to a majority-rule system which would be analogous to a legislative, rather than a contractual, system. This dispute about the nature of customary law continues to the present time, reflected in disputes as to the nature of opinio juris – whether it is a matter of individual and independent assessment, or a collective consciousness on the part of the international community as a whole. Over time, the persistent objector principle has been devised as a (somewhat awkward) means of papering over this division of opinion. Definitive resolution of the issue is not an immediate prospect.