Cooperating with evil? Accountability in peace operations and the evolution of the United Nations Human Rights Due Diligence Policy

International organizations (IOs) usually cooperate with national actors in order to implement global decisions and policies. This cooperation has become problematic as implementing partners have increasingly been accused of serious human rights violations. This article analyzes how implementing partners from the host state of a United Nations (UN) peace operation are held accountable. I argue that the complexity of contemporary peacekeeping limits the availability of traditional accountability mechanisms. I develop a conceptual model to demonstrate how, instead, different accountability forms interact and complement each other. I illustrate this interplay of accountability with a case study on the emergence of the UN Human Rights Due Diligence Policy (HRDDP). The accountability framework enacted by the Joint Human Rights Unit, the Special Procedures of the UN Human Rights Council and the International Criminal Court in the context of the UN peace operation in the Democratic Republic of the Congo threatened the legitimacy of UN peacekeeping. As a consequence, the UN adopted the HRDDP as a new, UN-based accountability mechanism to hold implementing partners from the host state of peace operations accountable.