The Responsibility to Protect (RtoP) has generated a great deal of discussion on armed humanitarian intervention in states in which human rights atrocities have been or may be occurring. In contrast, there has been little systematic analysis of the capacity-building role that the international community can play in states that struggle to provide a secure environment for populations within their borders. We have termed this international commitment to build the capacity of states to resist genocide and other mass human rights atrocities the 'Responsibility to Assist'. The international commitment given at the 2005 World Summit included helping all states live up to their obligations of human rights protection. In this chapter we examine how international and regional efforts to develop state capacity in policing (police capacity-building or 'police building') may assist a state to develop a culture of human rights protection, and thus reduce the likelihood of genocide, ethnic cleansing, war crimes or crimes against humanity occurring.