The doctrine of intertemporality prohibits the retroactive application of norms of international law in contentious proceedings and obliges the deciding court to positively ascertain the applicable historic rules. In situations in which the historic interaction between a European and a non-European entity needs to be litigated, problems arise. The applicable historic law is presently ascertained by recourse to specific (historic) European phenomena. In contentious proceedings, this methodology leads to a situation of »différend« – a situation in which the method of solving the dispute already vindicates the position of one of the parties to the dispute.