In this paper, I propose to investigate the utility of BITs in the formulation of customary international law in the area of state responsibility for the protection of alien property. It is my thesis that the frenetic conclusion of BITs is occasioned by the uncertainty that pervades international investment law since the advent of the developing countries on the international scene, and secondly, that international law has not kept pace with the developments that have taken place in the last thirty years in foreign direct investment. To the extend that this is so, I contend that each BIT is nothing but a lex specialis between parties designed to create a mutual regime of investment protection. In my view, such lex specialis is necessary simply because of the uncertainty in the law on investment protection but such uncertainty I humbly submit cannot be removed on a universal basis by these treaties as they do not consistently support defimite legal principles. On the other hand, it is my contention that the proliferation of BITs will help to confirm the present and indicate the possible future trends in international foreign investment law.