International Investment Law and Domestic Investment Rules: Tracing the Upstream and Downstream Flows

International investment law and domestic law governing foreign investment strongly influence one another and indeed operate in a relationship of co-dependency or interoperability. Yet the flows between the two bodies of law, and their respective modalities of influence, remain generally unexplored in international legal theory. To shed light on this important phenomenon, this article traces the ways in which international investment law can affect the content of domestic investment law, using theories of international law compliance as a lens for such an understanding. It then proposes a set of pathways by which domestic law can influence the content of international investment rules. International law thus depends upon national law not only for its implementation but for its very content. Indeed, the regime of investment law will not tolerate significant discrepancies between the two. An appreciation of this dynamic is critical to evaluating the prospects of improvements to international investment law and can inform the ongoing discussions among stakeholders to this end.