The Rule of Law, Standards of Review, and the Separation of Powers

Abstract This chapter analyses the extent to which separation of powers theories offer a useful framework to guide the approaches that tribunals take (or should take) to analysing deference to domestic decision-makers in investment treaty disputes. The separation of powers recognizes that decision-makers of structurally different institutional types will hold greater capacity to decide certain questions vis-à-vis others. The chapter highlights how such considerations might be relied upon by investment arbitrators to justify adopting deferential standards of review when examining the decisions of particular domestic actors, or the decisions of domestic actors on certain topics. To do so, the chapter first examines how separation of powers theories link to the concept of a rule of law. It then explores how such concepts might influence the approaches of investment tribunals to issues of deference in practice. The chapter further considers how separation of powers theories might be more directly engaged by investment tribunals to inform their approaches to deference, and so allow them to appraise and accommodate a separation of powers between domestic and international actors on a case-by-case basis.