International law makes it explicit that states shall not intervene militarily of otherwise in the affairs of other states; it is a central principle of the charter of the United Nations. But international law also provides an exception; when a conflict within a state poses a threat to international peace, military intervention by the UN may be warranted. (Indeed, the UN Charter provides for an international police force, though nothing has ever come of this provision.) The Charter and other UN documents also assert that human rights are to be protected—but in the past the responsibility for the protection of human rights has for the most part been allowed to rest on the government of the state where the violation of rights occurs. Not surprisingly in this context, the question of what protection (if any) should be provided by the UN or otherwise to individuals when their human rights are violated by their governments or with the complicity of their governments remains a contentious issue. Should the principle of respect for state sovereignty trump the principle of respect for human rights? In this volume contributors grapple with a specific case: was the North Atlantic Treaty Organization (NATO) intervention in Kosovo legally or morally acceptable? The contributors all have doubts on this score, and several argue strongly that the intervention was both legally and morally unjustified. A companion volume, Humanitarian Intervention: Moral and Philosophical Issues focuses on the philosophical principles involved in this sort of question; this volume, on the other hand, focuses as much or more on the political as on the philosophical.