Book excerpt: Within the context of an exponential proliferation of investment treaties with virtually uniform language and structure, The Interpretation of Investment Treaties by Trinh Hai Yen reveals the neglect or misapplication of international rules on treaty interpretation by tribunals in arbitral cases. Such practice has raised the question of the legitimacy of the interpretative process and the engendered inconsistent interpretations of investment treaties. The book proposes three interpretative approaches aimed at ensuring that adjudicators find legitimate meaning in the challenging generality and vagueness of investment treaty language. It also provides a comprehensive analysis of legislative solutions for states through a case study of the ASEAN Comprehensive Investment Agreement, as well as a comparative analysis of modern and traditional investment treaties.