Armed Conflicts and Customary International Law on Investment: Codification and Fragmentation of “Protection and Security”

The proliferation of investment treaties in international investment law has largely displaced the role of customary international law on investment protection. This paper considers the utility of customary international law during armed conflict and the compatibility in the interaction between treaty and customary obligations, through the classical norm of the host State to provide protection and security on foreign investment. Applying existing scholarship on the consequences flowing from the codification of customary law, this paper argues that the inclusion of protection and security clause in its codified form in treaties have diverged and fragmented from the original bare custom. Despite the fragmentation of protection and security in treaty rules, the corresponding customary law remains effective and would continue to govern the relationship between States in all circumstances, including armed conflict. This paper calls for a return to the bare custom on protection and security to facilitate parallel application of treaty and customary protection to achieve a universal scope and standard of foreign investment protection.