The legitimate expectation is a term invoked during State-investment dispute, when a foreign investor claims the frustration of his legitimate expectation under the breach of fair and equitable treatment. All arbitral tribunals consider the legitimate expectation as the main element of Fair and Equitable Treatment (FET). Usually, the frustration of the legitimate expectation is caused by the host State measure, whether this measure is among the normal regulatory measure of the State or the one that leads to indirect expropriation. Even though being used in investment dispute, the legitimate expectation is creating a huge controversy since it is facing debates on what concerns, its definition and legal basis. Therefore, this paper will attempt to assess the debate surrounding these issues concerning the concept of legitimate expectation.
