Most-Favoured-Nation Clause: Criteria of “Like Circumstances” and Its Relationship with National Treatment

This article examines the most-favoured-nation clause in international investment law, focusing on the criteria for determining “like circumstances” in the comparative assessment of treatment and on its delineation from national treatment. The study outlines the principal modalities of the clause’s operation, including its use as a treaty-based mechanism of comparison and as a potential basis for establishing less favourable treatment vis-à-vis investors from third States. It further argues for prioritising the analysis of the likeness of circumstances over purely formal indicators of the likeness of actors, and highlights the role of legal certainty and proportionality in assessing whether differential treatment may be justified where the host State exercises regulatory powers in pursuit of public interests.