The value of resorting to the flexible concept of experts on mission is strongly engrained in the United Nations’ pursuit of its institutional mandate. However, the discretion left to the Organization in the process is a potential source of disputes with its member states. Besides the 1946 Convention on the Privileges and Immunities of the United Nations, both the protection and the accountability system of experts has undergone little development since the creation of the United Nations. This article attempts to build the necessary framework for such a system, including by discussing its theoretical underpinnings as well as creating a hierarchy of authorities to settle disputes involving experts on mission. It departs from current ad hoc practices and advocates for a more robust approach that is based on the treaty text of the 1946 Convention but guided by a more realistic understanding of the role of experts.