The Legitimacy of Rules of Customary International Law and the Right to Justification
This contribution submits that although customary international law emanates from the free will of States, it is not State consent alone from which this source of international law draws its legitimacy. The common critique against the legitimacy of customary international law, focussing on the consent aspect, neglects that the legitimacy of customary international law derives also from its reciprocal nature and its generality. For this reason, this contribution explores whether the justice theory of the political philosopher Rainer Forst, the so-called Right to Justification, can provide a plausible explanation for the legitimacy of customary international law. According to this Right to Justification only norms that can be reciprocally and generally justified enjoy moral validity. These two features make it normatively acceptable for States to recognize the authority of customary international law.