The analysis of this thesis is to examine whether foreign investors can fully rely on the standard of FPS in BITs for the protection of their investments in the territories of host States which has been mandated to States by international law. This question cannot be answered without giving insights into the content and structure of the origin of FPS standard and adopts a dynamic based-perspective of the interpretation of FPS under VCLT 1969, encompassing the relationship between FPS and CIL. It investigates the tribunals' interpretation of the clause using case laws and literatures to identify and explore the underlying explanatory process behind tribunals' case findings and outcomes. The study examines the critical realism that the obligation of FPS standard does not place absolute liability to a host State, rather the exercise of a reasonable degree of vigilance. It evaluates the controversy surrounding the relationships between FPS and FET, and illuminates on how the two standards may co-evolve which has led to various arbitral tribunals' divergence opinions interpretation of the two principles. The evaluation of the application of FPS to digital assets is dynamic in this research as it addresses the nature of threats investors face globally today over cyber attacks of digital investments. The thesis also emphasis on balancing up investors' rights and obligation, which explains the measures that States can apply to prevent foreign investors from engaging in illegitimate activities. Having look at all these issues, circumstances, and the controversies surrounding FPS standard, the result found is that there is a existence of a gap in this area of the law, that would mean that foreign investors cannot completely rely on the principle of FPS for the protection of their investments in the territories of the host unless this lacunae is properly filled by both the States and arbitral tribunals, especially the tribunals' interpretative meaning of the standard of FPS.

Die Beilegung von Investitionsstreitigkeit erfolgt innerhalb des ICSID-Systems durch die nicht ständigen und für jeden Fall neu gebildeten ICSID-Schiedsgerichte. Mit Institutionen zur Sicherung der homogenen Entwicklung der Rechtsprechung wie die EG-Generalanwälte, die EG-Vorabentscheidung, das WTO-„Appellate Body“ oder die einem Berufungsverfahren gleichstehende Verweisung an die Große Kammer des EMRGH ist allerdings das ICSID-System nicht ausgestattet. Vielmehr ist die Möglichkeit einer Berufung innerhalb des ICSID-Systems ausdrücklich ausgeschlossen. In der vorliegenden Arbeit wird die Homogenität der ICSID-Rechtsprechung geprüft, um festzustellen, ob die Rechtsprechung der für jeden Fall neu gebildeten ICSID-Schiedsgerichte derartige Dissonanzen aufweist, die das ICSID-System reformbedürftig machen. Die Prüfung der Homogenität der ICSID-Rechtsprechung bezieht sich auf die Auslegung von gleichen bzw. ähnlichen Bestimmungen völkerrechtlicher Investitionsschutzabkommen sowie des ICSID-Übereinkommens selbst durch die ICSID-Schiedsgerichte und betrifft im einzelnen die folgenden Themen: (a) Definition des Begriffs „Investition“ im Sinne des ICSID-Übereinkommens. (b) Ausdehnung der Reichweite der Meistbegünstigungsklausel auf Verfahrensvorschriften. (c) Zuständigkeit der ICSID-Schiedsgerichte für reine Verletzungen von Investitionsverträgen mittels weiter Streitbeilegungsvorschriften und Regenschirmklauseln. (d) Standard der Enteignungsentschädigung und Unterscheidung zwischen indirekter Enteignung und staatlicher Regulierung. (e) Völkervertraglicher und völkergewohnheitsrechtlicher Notstand. Die Untersuchung kommt zu dem Ergebnis, dass die ICSID-Rechtsprechung an Heterogenität leidet. Dementsprechend bildet der Mangel an Mechanismen zur Sicherung der Homogenität der ICSID-Rechtsprechung ein schwerwiegendes institutionelles Defizit. Es ist daher dringend, dass das ICSID-System unmittelbar reformiert wird, vorzugsweise durch die Schaffung einer ICSID-Berufungsinstanz. / The settlement of investment disputes within the ICSID system is carried out by the ICSID arbitral tribunals which are non-permanent judicial bodies. Every separate case is adjudicated by a different tribunal. The ICSID system, however, does not provide for any institutions similar to the EC Advocate Generals, the EC preliminary rulings, the WTO Appellate Body or to the appeal-like process of the referral to the Grand Chamber of the ECHR capable of securing the homogenous development of the case-law. Moreover, the possibility of appeal of an arbitral award is explicitly excluded within the ICSID system. The present thesis examines the homogeneity of the ICSID jurisprudence in order to ascertain whether the case-law of the separate and not standing ICSID panels proves to be so inconsistent that the ICSID system is in need of reform. The study of the homogeneity of the ICSID jurisprudence concerns the interpretation of identical and similar provisions laid down in international investment treaties as well as of the ICSID Convention itself by the ICSID panels. In particular, it deals with the following topics: (a) Definition of the term “investment” pursuant to the ICSID Convention. (b) Extension of the scope of application of the most-favoured-nation clause to procedural provisions. (c) Jurisdiction of ICSID tribunals over mere violations of an investment contract through broad dispute settlement clauses and umbrella clauses. (d) Standard of compensation for expropriation and distinction between indirect expropriation and state regulation. (e) State of necessity under customary and investment treaty law. This study comes to the conclusion that the ICSID jurisprudence suffers from heterogeneity. Thus, the lack of mechanisms able to secure the consistency of the ICSID case-law constitutes a serious institutional deficit. It is, therefore, urgent to reform the ICSID system immediately, preferably by way of establishing an ICSID appellate authority.