This sequel examines the roles of the UN in its implementation of the laws of war. Reference to the UN in laws of war treaties before 1980 was always in connection with implementation. They related to such issues as chemical weapons, the safety of UN and associated personnel, land and anti-personnel mines. All put a burden on the UN to obtain prompt agreement. The International Court of Justice has a long record but is limited by the reluctance of states to allow a remote court to settle their interests. Since the early 1980s, the UN Security Council has had an important role in implementation matters but only selectively: in the 1990s, for example, over Kuwait, former Yugoslavia and Rwanda. War criminals are hard to pursue. There are twelve lessons to be learned from the incomplete and flawed transition from a state-based system of implementation to one encompassing broad UN-based elements as well. The difficulties have become apparent in the conference in Rome to establish an International Criminal Court.