I discuss a remark made by Gitta Sereny about Treblinka Kommandant Franz Stangl that questions the role and scope of moral authority, viz. “I don’t know now at which point one human being can make the moral decision for another that he should have the courage to risk death.” I provide an illustrative elaboration from her remark of a role for moral authority and a limit on its scope. First, I use the idea of supererogation to introduce the idea and role of moral authority. Second, I argue that there is a parallel understanding of Sereny’s remark that shows moral authority operative in a similar role in Stangl’s case. Third, I make four refinements to what she has expressed about Stangl, each of which further illuminates the nature of moral authority. Finally, I address objections and consider the implications of my account.