1 Introduction

1.01 Most international adjudications involving States feature disputes that concern the meaning of treaty provisions.1 This phenomenon is in large measure attributable to the imperfections of language and the ineffable quality of human interaction. Practical necessity has thus dictated that principles or rules2 of treaty interpretation assume an important role resolving differences between States and, increasingly, between States and private investors. Notwithstanding their practical importance, treaty interpretation rules have not developed—and are unlikely ever...