Legality – the ‘spirit or way of thinking characteristic of the legal profession’ or the ‘quality of being legal or in conformity with the law’ – is a condition with which international lawyers might be expected to exhibit relative comfort. Not so. Far from naming common ground upon which international lawyers routinely assemble, legality marks a site of intense and unresolved conflict. It is a condition that international lawyers aspire to secure, and perennially worry about failing to bring about. This chapter demonstrates how international law’s fraught sense of legality is crafted and experienced by attention to a highly controversial judicial ruling – that of the International Court of Justice (ICJ), in July 1966, in the South West Africa cases. It writes legality as an incident of experimental practice that entails making ‘fictional’ a politics of norms and normalcy. It does so drawing upon the experience of ‘fiction’ with which Michel Foucault experimented in his later work.