IT was in 2005 that the United Nations, celebrating its 60th anniversary, adopted, by consensus, a resolution on the principle of Responsibility to Protect (R2P). The initiative was a response to the international community’s failures to prevent the genocides in Rwanda and the massacre at Srebrenica in the 1990s. The principle established that sovereignty is not absolute and that states have a primary responsibility to protect populations everywhere from mass atrocity crimes: genocide, war crimes, ethnic cleansing and crimes against humanity. If a state failed in this responsibility, the international community had the duty to take collective action. Despite its...