This Chapter provides an overview of the two broad types of control that arbitral tribunals exercise over proceedings in state courts. First, in both international commercial arbitration and investment treaty arbitration, arbitral tribunals may exercise indirect control over state courts through their jurisdiction over the parties before them as part of their inherent power to protect the integrity of the arbitral proceedings. They do so through the issuance of provisional measures, typically in the form of anti-suit injunctions. In this context, investment treaty tribunals have the additional power to issue measures addressed directly to the host state courts. Second, and uniquely to tribunals established pursuant to investment treaties, the activities of the judiciary may come within the exercise of principal jurisdiction by the arbitral tribunal. Under investment treaties, the tribunal may be seized with a claim for international responsibility arising out of measures taken by a state’s courts which can be broadly organised into two categories: expropriatory and non-expropriatory claims as a result of the improper administration of justice.