The International Law Commission and the Development of International Investment Law

International investment law has assumed an increasing prominence
largely due to the proliferation of investment treaties and the number of
arbitral awards made thereunder. Yet, there are many core questions
that remain to be authoritatively answered. This Article considers the
nature of the divergences in investment treaty jurisprudence and the role
that the International Law Commission (ILC) could potentially play in
contributing to the coherent development of international investment
law. The Article argues that some areas of international investment law
are more appropriate for attention by the ILC than others. It draws a
distinction between those aspects of international investment that only
have a basis in treaty law and those aspects of international investment
law that are underpinned by common standards stemming from custom-
ary international law or general principles of law.
The Article argues that international investment scholars cannot nec-
essarily expect the convergence of jurisprudence in the context of treaty
provisions that have been specifically negotiated by the parties, as these
provisions must be interpreted on a case-by-case basis. This means that
topics like the most-favored-nation (MFN) clause are less suitable for cod-
ification, as the meaning of these provisions will often depend on the
particular context of the treaty and the precise intentions of the parties.
In contrast, there is a stronger case for the codification of international
investment law where common standards exist. The Article therefore
considers the formation and development of customary international law
in relation to investment protection. It argues that while investment
treaty tribunals have struggled with the identification of customary inter-
national law in this area, the ILC could play a central role in clarifying
the state of the relevant rules and principles, in furtherance of its core
mandate of promoting the progressive development and codification of
international law.