As the edifice of international law expands in many various policy areas, the number of international norms that penetrate into the domestic legal orders of states is also increasing. That is because, the implementation of international norms requires states to give effect to those norms within their jurisdiction by exercising their sovereignty and adopting the necessary measures. Therefore, despite the changing paradigms in the international setting, international legal order still operates on the basis of the states’ ability to exercise their sovereign functions. Moving on from this premise, this thesis argues that state sovereignty, as conceptualised in the modern international legal context, may assist in the interpretation of certain international obligations of the state by way of necessary implication. That is the case with the interpretation of what is described as standard-setting obligations of the state. In other words, the fact that the bearer of an international obligation is a state with a sovereign capacity having sovereign functions does shape the content of standard-setting obligations of the state. In an effort to demonstrate how sovereignty may play out in the interpretation of such obligations, this thesis takes a closer and critical look at the recent trends in investment treaty-making practice and the expanding scholarship on standard of review approaches in international investment law. It concludes that the proposed interpretive approach based on the doctrine of necessary implication offers a better and systematic method to accommodate the regulatory autonomy of the state in the assessment of state responsibility under investment treaty standards.