"Qui peut et n'empesche, pesche", Loysel. ( He who can but does not prevent, sins). This adage of pre-revolutionary French law has its equivalent, mutatis mutandis, in all systems of law. Even if, as a matter of international law there is no requirement of fault in order to engage international responsibility, the violation by an international legal person of one or more of its obligations may arise just as easily from passivity as from a positive course of action: international legal persons are responsible both for their actions and their omissions insofar as they constitute internationally wrongful acts. In the Corfu Channel case, the International Court clearly distinguished the wrongful acts of the United Kingdom from the equally wrongful omissions of Albania. The notions of action and omission give form to, and puts some meat on the bones of, the notion of the “internationally wrongful act”, a notion which was deliberately left skeletal. While internationally wrongful acts and omissions in international law may be relatively easy to define, the dividing line between the two categories is sometimes difficult to identify (section 1). However, the consequences attached to the distinction for the purposes of the regime of international responsibility are in any case relatively limited (section 2).