Mainly in reaction to the use of torture by the United States after the attacks of 9/11, international relations scholars began asking under which circumstances the content of an international norm changes and at which point it becomes void of its normative content if it is repeatedly violated, a concept known as “norm erosion”. International lawyers have until very recently not engaged with this debate. This working paper aims to change that by looking at the example of the prohibition of torture to display legal scholarship perspectives on how norms of treaty law and customary law come into being, how treaties can be modified or renounced, how customary law can be changed, as well as how re-interpretation processes take place that may affect a rule’s content, scope and effect. Furthermore, international relations research has developed criteria which allow to determine whether a certain norm is more robust and thus resilient to change and erosion. These criteria also find a correspondence in the rules of international law and can be translated to, and framed in, international law terms. The findings from the perspective of international law reinforce international relations research which has identified the prohibition of torture to be very robust and resilient. Also, both disciplines underline that pure non-compliance does neither lead to norm change nor to norm erosion. Although international law has not played a decisive role in most international relations research on norm erosion, in the end, both disciplines still arrive at similar explanations under which circumstances norm change and norm erosion take place. Through uncovering this, the working paper also demonstrates how interdisciplinary scholarship may strengthen mono-disciplinary scholarship by arriving at the same conclusions via different avenues.
