This book surveys and analyses the nature of FET as a "new" rule of customary law that is non-contingent and absolute in that it protects a given entity irrespective of the treatment which may be accorded to others. The author explores whether the often-heard criticism of the international investment protection regime is justified. The overarching questions are: Does the system's mixture of private arbitration and public law indeed undermine accountability and independence in judicial decision-making? Does it trump principles of legislative supremacy and, in the end, alter a central tenet of representative democracy? Among the far-reaching aspects of the subject covered are the following: the relationship of FET to human rights and other standards of protection; assumptions about reciprocity and mutuality; the "treatification" of foreign investment law; the special significance of the Energy Charter Treaty; ICSID as a self-contained system; identifying limitations on the parties' freedom of choice; the protection of legitimate expectations; the relevance of investors' conduct in FET proceedings; due process in administrative decision-making, and denial of judicial justice. Relevant case law is examined, and there are detailed descriptions of the main dispute resolution forums – ICSID arbitration especially, but with due attention to the new UNCITRAL, the ICC Rules, the SCC and the LCIA Rules. This is a significant contribution to the debate over a controversial concept and its normative underpinnings. By analysing how states are bound by investment treaty obligations and how arbitrators deal with them, this book explains how the standards are continually shaped and scrutinized to respond to the needs of the actors engaged in an investment relationship.