An investor-State tribunal enjoys significant authority once a dispute is referred to it. Among a tribunal’s unquestioned powers is the power to order interim relief— including with respect to the most sovereign of a State’s conduct: its enforcement of its criminal law. In exercising these powers, an investor-State tribunal goes beyond the role traditionally assigned to it—i.e. to award damages for prejudice caused by a treaty breach—and dictates sovereign conduct. While the applicable treaty, arbitral rules, or law of the seat may not offer specific instructions, arbitral tribunals deciding on such interim relief requests can rely on a significant body of case law. That case law reflects a coherent approach to a thorny question, even though outcomes may vary. This article will deconstruct that coherent approach—from the foundations of the tribunal’s authority to order interim relief in respect to pendant criminal proceedings, to the rights that such relief may protect, to the requirements for ordering such relief, as well the effect of such relief and its duration in addition to any recourse for non-compliance.