Systemic Integration and International Investment Law – Some Practical Reflections

This paper takes an empirical, practical approach to test the proposition that systemic integration leads to greater coherence of international law. It builds on work by Professor Campbell McLachlan and others that specific treaty-based regimes can be located in the broader context of international law through art 31(3)(c) of the Vienna Convention on the Law of Treaties. The paper analyses the Argentina investment treaty arbitration cases involving necessity to establish whether systemic integration principles can be regarded as realistically capable of influencing coherent outcomes in similar cases. It concludes that the evidence does not support the notion of systemic integration as being outcome determinative, and thus does not support the notion of systemic integration as a genuinely cohering mechanism for international investment law. What does this mean for how we think about international law generally? A positivist account of international law is opposed. The Argentina necessity cases support a more realist account of “practical reasoning”, which is perhaps more helpful than systemic integration theory in understanding the jurisprudence of international law. It is helpful to have procedural mechanisms so that tribunals and other international decision-makers can have regard to other areas of international law, and proper that these be provided for expressly, as in art 31(3)(c). However, the strong form of the systemic integration argument – which elevates those procedural mechanisms into a deductive argument that international law is a coherent whole – should be resisted. Whilst it is likely that the doctrine of necessity for international investment law will be synthesised over time as leading awards, textbook opinion and state practice converges on the nuances of an approach as applied to concrete economic situations, this is a messy and practical, and not an endogenous and deductive, endeavour