This article reviews the Iron Rhine case before an arbitral tribunal established under the rules of the Permanent Court of Arbitration. It inquires how an old peace treaty is interpreted to resolve a current dispute with the help of the principle of sustainable development. Three points of law are critically assessed. Firstly, the way in which the tribunal establishes its jurisdiction vis-à-vis the ECJ. Secondly, how it determined the applicability of the treaty of separation. And finally, in which way it employed the principle of sustainable development. The article concludes by reflecting on the way in which judgments and awards should be understood and discussed by legal scientists.