Investment tribunals are often alarmed for giving different interpretations to similar questions of treaty interpretation. This, in turn, gives rise to jurisprudential inconsistency in international investment law. Inconsistency in decision making is the nemesis of any dispute settlement mechanism, and has accordingly given rise to legitimacy concerns against the investor-state dispute settlement (“ISDS”) mechanism. This has caused stakeholders to call for reforms to address the interpretative inconsistency plaguing the ISDS mechanism. While some of the reforms seek to find solutions within the existing ISDS mechanism, other more extreme ones seek an overhaul of the ISDS mechanism itself. While each proposal has its own positives and negatives, their underlying objective is the same i.e., to ensure predictability, consistency and coherence in decision making and avoiding inconsistent decisions. Any reform to the ISDS mechanism would require all stakeholders to carefully consider the issue, as well as the scope, nature, and reasonableness of each potential reform. In this context, this article explores the currently debated questions of interpretative inconsistencies at a granular level, critically reviewing the approaches taken by tribunals in succeeding arbitral awards. It also analyses the various proposed front-end and back-end solutions for tackling such inconsistency. Lastly, the authors propose solutions: a concrete standard of review and an interpretative methodology to preserve the legitimacy of international investment law.

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