This book addresses the disparity between positive non-treaty law and its scholarly assessment in the area of moral concepts, understood as altruistic as opposed to reciprocal legal obligations. It shows how scholars are generously willing to assert the existence of a rule of international law, thereby moving further away from actual state practice, not taking into account the factors of legal rhetoric and the core survival interests of the state in the formation of custom and general principles of law. The main argument is that such moral concepts can simply not manifest themselves as non-treaty sources of international law from a dogmatic perspective. The reason is the inherent connection between the formation of the non-treaty sources of international law and state interest that makes it difficult, if not impossible, to assess state practice or opinio juris in the case of altruistic obligations. The book further demonstrates this finding by looking at two cases in point: Human rights and humanitarian exceptions to the prohibition of force. As opposed to the majority of existing works on the subject, State Interest and the Sources of International Law takes a bigger-picture approach to a number of distinct problems in international law scholarship by looking at the building blocks of international relations on the one hand, and merging this with sources doctrine on the other. It will be of interest to researchers, academics, and students in the fields of international law, human rights, international relations, political science, legal philosophy, and legal theory.