PRODUCT DESCRIPTION The purpose of this work is to examine the impact of Bilateral Investment Treaties (BITs) as instruments governing the treatment of foreign investment. The historical doctrinal divide between capital- exporting and capital importing states (Hull Rule versus Calvo Doctrine) is highlighted at length, especially within the context of multilateral failures and bilateral successes that culminated with BITs proliferating as the customary International Law on International Investment.The consensus on BITs is an achievement that presents a paradox. The work also looks at the significant role of arbitration mechanism (privatisation of International Law) by weighing on the dilemma calculations increasingly faced by host states. The conflicting positions of arbitration tribunals notwithstanding, the fact that they have all acknowledged the necessity defense as not limited solely to military action lends great support to the argument that a state whose essential security interests is under threat be precluded from wrongdoing if it adopts necessary measures in breach of the treaty to bring the crisis under control.