SummaryDiscussion surrounding the prevention of genocide has focused to a large extent on the appropriate mode(s) of reaction to particularly serious breaches of human rights obligations. In particular, the question arose whether existing UN mechanisms aimed at preserving international peace and security should be regarded as a privileged — or even exclusive — means to enforce compliance by states with their obligations relating to genocide. Drawing extensively on the work of the International Law Commission on the codification of the law of state responsibility, the author argues that the new draft articles, with their emphasis on “serious breaches of obligations arising under peremptory norms of general international law” rather than obligations erga omnes, are ill-suited to provide for the taking of preventive measures by “not-directly affected” states. Paradoxically, the institutionalization of mechanisms for preventing gross human rights abuses has been reduced to a minimum in the new draft, with emphasis being laid on the vague requirement that states “cooperate” to bring “serious breaches” to an end. It is suggested, however, that ascribing a subsidiary role to UN organs and procedures is, despite criticisms made as to their adequacy, necessary to supplement state action. The UN has in fact a distinct legal interest that is clearly affected when breaches of obligations relating to genocide occur. More importantly, by acting on behalf of the “organized international community” in matters of international peace and security, the Security Council has itself assumed today a legally binding subsidiary obligation to prevent genocide. The article concludes that in the absence of ineffective decisional institutions for the prevention of genocide, the choice is not between the subjectivism of a decentralized response and the absence of any consequences for the most serious wrongful acts but rather to strengthen the UN’s institutional capacity to react.