In 2004, major problems of sexual exploitation and abuse by UN peacekeepers in the Democratic Republic of the Congo and other operations became a public scandal for the United Nations. Before that story broke, the Future of Peace Operations Program (FOPO) had begun work on the problem of criminal accountability for personnel in peace operations. Because states retain disciplinary responsibility for their military forces in peace operations, that work focused on UN staff and experts on mission, a category that includes UN police. As operations become more deeply involved in assisting or substituting for local government, their personnel must themselves be subject to the rule of law, and be seen as subject to it by local peoples. However, in Improving Criminal Accountability in United Nations Peace Operations, FOPO found that the tenuous reach of the law covering criminal acts by UN personnel on mission has left a legal and procedural vacuum filled only in part by administrative sanctions (such as fines, dismissal, and/or repatriation) for actions that would be felonies under most states’ domestic laws. FOPO therefore looked into other options, some of which would require serious rethinking of criminal jurisdiction in and for peace operations.