This article considers the role of national courts in investment treaty arbitrations between an investor and a host-State. While the ICSID arbitration regime provides for an a-national approach, the choice of alternative arbitral institutions or rules in an investment treaty could bring into issue the role of the courts of the place of arbitration. It is suggested that the involvement of a sovereign State as a party to such arbitration proceedings raises issues of state immunity not encountered in international commercial arbitrations. While an agreement in an investment treaty to arbitrate an investor-state dispute confers jurisdiction on an arbitral tribunal to determine the dispute, there is presently no global consensus that such an agreement alone amounts to a waiver of immunity of the host-State from the jurisdiction of other national Courts. Absent such waiver of jurisdiction, the court of the place of arbitration would lack legitimacy to exercise any ‘supervisory’ jurisdiction over the host-State party to ensure compliance under its domestic legislation. The authors suggest that national legislatures should consider this when reviewing applicable domestic laws on international arbitration and state immunity. Treaty negotiators should be aware as well of such limitations. State immunity, waiver of immunity, investment arbitration agreement, investor-State dispute, international arbitration, immunity from jurisdiction, court of the seat, supervisory jurisdiction