Research on the Legitimate Expectation Principle in International Investment Arbitration

The legitimate expectation principle, as an important legal principle developed in the practice of international investment arbitration, originated from the concept of reliance protection in domestic administrative law of countries like the UK and the US. Currently, in investment arbitration, more and more arbitration tribunals regard the legitimate expectation principle as one of the significant considerations for interpreting the fair and equitable treatment clauses. However, due to the ambiguity of the principle itself, there is still no unified interpretation and regulation on the application requirements of this principle in the academic circle and practice. Therefore, this paper studies the legal basis of the legitimate expectation principle in domestic and international law, discusses the advantages of its application, compares various academic viewpoints, and finally proposes three core application requirements of this principle. The intention is to establish a standardized criterion for the determination of reasonable expectation, narrow the differences in the application of the principle by arbitration tribunals, achieve the legal unity and practical coordination of it, thereby limiting the arbitration tribunal's discretionary power, balancing the interests between investors and host countries, and promoting the good development of international investment rule of law.