Inside the treaty interpreter’s mind: An experimental linguistic approach to international law

Abstract One particularly intense critical debate over interpretation in international law concerns the role of moral factors – specifically, the degree to which such factors influence legal interpretation, and how the law should deal with them. A formalist approach argues that moral considerations should be excluded as non-legal; a critical legal studies approach suggests they are an inevitable part of the functioning of international law and must therefore be acknowledged; and an inclusivist approach would suggest their influence is permissible, albeit only under certain circumstances. In this article, we are concerned with the question of whether moral factors influence interpretation at all, taking international treaties as the object of study. To address this question, we take a novel approach, proposing an experimental linguistic framework to test whether linguistic categorizations (originally developed for the analysis of everyday language) can be successfully applied to treaty interpretation, relying on both laypersons and experts as participants. Although some caveats must be made, the experiments deliver clear results: both groups are influenced by morals in their interpretation of international treaty norms. On this basis, we draw conclusions regarding (i) how the process of interpretation of international law operates; and (ii) what the institutions managing that process, such as courts, should factor-in when deliberating their decisions. By adopting this novel perspective, we also contribute to linguistic and experimental approaches to international law at the methodological level.