This chapter investigates whether the in-built asymmetry of treaty-based investor−state arbitration runs counter to the rule of law. While there is a rich literature (empirically) studying the effects of investment treaties on the rule of law, few studies have addressed whether treaty-based investment arbitration itself has the qualities of the rule of law. Studies addressing this latter question focus mainly on issues of judicial independence of arbitrators and the coherence of the arbitration legal system. However, the question of the compatibility of the asymmetrical structure of the investment arbitration system with the rule of law remains underexplored. This chapter aims at filling this gap by assessing whether entrusting only investors with the procedural rights of challenging states before arbitration tribunals is compatible with the rule of law in its own terms.