This thesis is a political history of the trials of wartime collaborators in Norway after 1945. It offers a first scholarly investigation into the central actors behind these trials, looking at the ways in which Norwegian authorities planned, implemented and interpreted the ‘reckoning’ with wartime collaborators between 1941 and 1964. In doing so, it evaluates the broader political purposes the trials served, how these changed over time, and the mechanisms that brought about these changes. The analysis distinguishes between ‘internal’ and ‘external’ influences on the trials. ‘Internal’ influences are understood to be both the inherent doctrinal and institutional limitations of the law, as well as the personal and political convictions found within the authorities that governed the trials. ‘External’ influences meanwhile constitute the broader public attitudes and debates surrounding the trials in politics, the media and civil society. This thesis therefore seeks to deepen our understanding of the trials in two ways. Firstly, it goes beyond existing scholarship by focusing not on questions of ‘morality’ and ‘justice’, but instead on competing institutional dynamics and political representations of legitimacy and authority. Secondly, unlike most previous scholarship, it provides an encompassing account of the policy decisions underlying the trials by looking at the full timespan of the Norwegian authorities’ administrative engagement with them, from their initial conceptualisation to the handling of their legacy. Thereby, individual decisions and events can be seen in relation to one another, allowing us to understand what purposes the trials served at different stages of their implementation, and how legal and administrative measures related to their political purposes. In response to previous scholarship on the trials, this thesis argues that the driving agent of the trials was not the static agenda of any one institution or group, but that their final shape was the result of the complex interaction of demands for legal consistency with a rapidly changing political and social context, both at the national and the international level.