International dispute resolution mechanisms do not exist in vacuum. Their design and functioning are strongly influenced by political, legal and functional considerations. Any attempt to understand their systemic implications thus requires more than an analysis of their constituting instruments. The chapter analyses the EU’s move towards the judicialization of traditional investor-State dispute settlement (ISDS) mechanisms and its hurdles. To this aim, the chapter firstly reviews the ‘constitutional’ rationale behind the judicialization of arbitral ISDS in the light of the Union’s legal development and nature. It then moves on to analyse the potential systemic challenges that arise from the attempt to transplant that same rationale into the international relations of the EU. Among these challenges, particular importance has been given to the highly value-based concept of ‘justice’ underlying the judicialization of ISDS, which greatly impinges in the sensitivity of States and their populations.