Aidōs and dikē in international humanitarian law: Is IHL a legal or a moral system?

Even though International Humanitarian Law (IHL) is, strictly speaking, a branch of international law serving as the body of laws governing the conduct of armed conflicts, it functions also, and perhaps to a greater extent, as a moral system (either followed or rejected) for the armies involved in armed conflicts. As utilitarians already noticed, the development of legal systems was powerfully influenced by moral opinion, and conversely, moral standards had been profoundly influenced by law, so that the content of many legal rules mirrored moral rules or principles. Law, like morality, is interested in creating a good society: enabling people to live together in a community and inculcating a sense of social responsibility. However, despite these similarities between the systems, law and morality differ in some of their objectives and in the methods they use for achieving their goals and sustaining human behavior. The application of this conclusion to IHL and the analysis of both its historical nascence in the nineteenth century and the philosophical concepts informing it suggests that IHL serves more the purposes of a moral system than those of a legal system. This claim is strengthened by the analysis of two examples of legal rules of IHL: the proportionality principle in causing collateral damage and the instruction that preventive (or targeted) killings should be used as a last resort.