The Investment Court System is the core feature of the EU international investment policy. In its Opinion 1/17 the CJEU confirmed the legality of the new ICS in CETA under EU law, providing important legal and policy implications for the future co-existence of EU law and international investment law. This chapter offers a critical assessment of the ICS, examined through the CJEU’s reasoning in Opinion 1/17. First, we discuss the nature of the ICS in relation to the EU judicial system. Second, we consider the effects of the ICS on the autonomy of the CJEU and the interpretation of EU law. Finally, we focus on the main features of the ICS in light of the rule-of-law criteria, as the core EU value. Where relevant, the CJEU’s Opinion is supplemented by remarks of late Advocate General Bot, which uncover a number of relevant political considerations. The design and functioning of the ICS thus provide important insights into the EU’s understanding of the rule of law in international investment law, which is ultimately envisaged to be implemented through a Multilateral Investment Court.