Fair and equitable treatment is a central norm in international investment law. This norm is contained in the vast majority of international investment agreements as one of the main standards for the protection of foreign investors. Historically, international investment agreements contained short and general clauses of fair and equitable treatment, which were formulated either as free-standing provisions with a reference to general international law, or to the international minimum standard of customary international law. Especially since the first decade of the 21st century, drafting approaches to fair and equitable treatment became increasingly diverse and generated complex and elaborate clauses seeking to address the different elements of the norm that have developed over time. The drafting approaches reflect the long-standing controversies with regard to fair and equitable treatment and the question of whether this concept is to be constructed in accordance with the international minimum standard or as an independent and self-contained standard possibly exceeding customary international law. Both concepts have remained vague and have created difficulties in the interpretation of fair and equitable treatment, which due to its general character became a prominent cause of action in investor-state arbitration proceedings. The evolution of arbitral jurisprudence stimulated the emergence of different elements of fair and equitable treatment, including the protection of the investor’s legitimate expectations, the protection against discrimination and arbitrary treatments, and the principles of due process, denial of justice, and transparency. The increasing number of cases on the basis of fair and equitable treatment also led to concerns and criticism that a far-reaching concept of the norm would threaten the host states’ sovereignty and their right to regulate, as well as the principle of sustainable development. These concerns and the fact that a growing number of investment disputes were brought against developed countries motivated first the North American Free Trade Agreement member states and subsequently other states and the European Union to adapt their international investment agreements in order to try to concretize the concept of fair and equitable treatment and to limit the discretion of arbitrators. The concept of fair and equitable treatment has also received considerable attention by scholars who propose a variety of different approaches to the interpretation of the norm and the balancing of the conflicting private and public interests at stake.
Minimum Standard of Treatment of Aliens, Fair and Equitable Treatment of Foreign Investors, Customary International Law and the Diallo Case before the International Court of Justice