While histories of human rights have proliferated in recent decades, little attention has been given to the history of thinking about duties to protect these rights beyond sovereign borders. We have a good understanding of the history of duties of sovereign states to ensure the safety and well-being of their own citizens and of the right of other states to forcefully intervene when these duties are violated. But the story of the development of thinking about duties to assist and protect the vulnerable beyond borders remains to be told. This article defends the importance of excavating and examining past thinking about these duties. It then sketches key aspects of Western natural law thinking about such duties, from Francisco de Vitoria through to Immanuel Kant, claiming that such study holds the promise of exposing from where ideas that prevail in international law and politics have come and retrieving alternative ideas that have been long forgotten but that may reward renewed consideration. It concludes by briefly outlining how three such retrieved ideas might be of particular use for those seeking to push international law and politics in a more just direction today.