International law governing international armed conflict has grown since 1945 to include many crimes for which individuals may be held criminally liable. The ICTY and its supporters claim that much of this law has been extended to non-international armed conflict. Nevertheless, states have resisted the extension. The two domains of war are too different, legally and politically, for any simple extension of the law. What, really, has caused the rapid growth of internal-armed-conflict law at the ICTY? The answer given in this paper is that it has been accomplished by an ICTY moral philosophy masquerading as method. The tribunal’s judges, free from state or legislative oversight, proceeded almost immediately after the institution’s establishment to create a legal code for non-international armed conflict. They were well aware that the majority of states - which ultimately decide the substance of international law - were, as late as 1977, opposed to or had doubts about, such expansionism. Under a veneer of legality, a humanitarian sentiment that had been blocked by states at the diplomatic conferences convened by the ICRC found an opening with the establishment of the ICTY. Some of the very people who had been most vocal about the moral deficiency of the states’ position obtained senior appointments at the new tribunal. In the name of a kinder and fairer world for victims of civil war, what had been a regulatory desert in international law was systematically populated with criminal-law rules transposed from the field of international humanitarian law. Can the ICTY’s law survive in the long term against the power of sovereign interest? I consider this question in the light of the United States’ critique of the ICRC’s 2005 customary-law study.