This article examines a piece of early medieval Irish law, the Cáin Adomnáin, considering it in the context of the endemic violence in the Irish society of the 7th and 8th centuries. We argue that the Cáin was an attempt by secular and religious leaders of the period to offer distinctive protection for women, children and clerics which advanced contemporary legal and political standards of protection. We conclude that the Cáin illustrates the potential for the application of humanitarian principles in distinctive cultural, legal and religious settings and traditions and that it deserves to be remembered as part of the heritage of international humanitarian law.