In the 1986 Nicaragua case, the International Court of Justice famously took the view that two additional criteria exist in customary international law for the exercise of collective self-defence, alongside the criteria that it shares with individual self-defence. These purported additional criteria have been commonly repeated in scholarship since. First, it is said that the state that has been attacked must ‘declare’ that it has been so attacked. Second, it must ‘request’ aid in its defence. This chapter sets out the manner in which the Court identified these requirements and whether it considered them to be legally determinative or merely evidentiary. It then goes on to examine state practice/opinio juris, to test whether the requirements indeed can be identified as rules of customary international law. It is argued that the first of those asserted requirements and declaration, in fact, has no legal basis. In contrast, it is argued that the issuance of a request is, as the Court indicated, a binding requirement for the exercise of collective self-defence.