Abstract
This master's thesis looks at the current stand of international investment law with regard to the perceived colliding of interests between foreign investor protection and host states’ right to regulate. At the beginning of this millennium, this conflict was solved rather differently by various investment tribunals. By analysing the relevant awards of 2016 this thesis shows that investment tribunals now address the issue in a more uniform way and that they take account of public welfare as well as the foreign investor. The current doctrine of international invest-ment law thus seems to be more balanced. The principle of proportionality is an important concept in this thesis as the analysis of the investment awards of 2016 is conducted through the lens of this principle. This thesis argues that the principle of proportionality merely is a semantic structure explaining ordinary legal reasoning; the criteria of suitability and necessity establishes whether a legitimate legal conflict of rights and interests exists and the criterion of proportionality in the narrow sense orders these rights and interests according to the underlying legal doctrine. The analysis of the international investment awards of 2016 is both an assessment of whether and how interna-tional investment tribunals explicitly apply the technique of the principle of proportionality, as well as an investigation of whether the semantic structure of the principle of proportionality explains the tribunals’ reasoning.