Elementarily, at least within the business environment, any discussions regarding an economic activity posit international trade and investment to be connected. Even to the discerning economist, businessman or policy maker, transfer of goods from one point to the other, provisions of services and direct investment ought to, rationally, be covered in one and the same agreement. However, this has not been possible under international law despite evident historical reasons approving such. International law manages trade and investment independently of each other. The separation of trade and investment has both historical and economic undertones that eventually led to the development of bifurcation in the legal regimes that regulate them. Though some commentators argued that the objectives of the two regimes are different, reality dictates otherwise, as both are seen to be ultimately deeply concerned with efficiency and the liberalization of economic activities; as such the investor and/or trader are not oblivious of the protections provided by the regimes of international trade and international investment law. So should the chicken come home to roost? The principle of non-discrimination, which offers the relative substantive standards of treatment, is at the heart of international economic law and is present in both regimes but has, at the same time, been interpreted and applied incoherently and inconsistently in both, significantly more in investment law than in trade law. As such, this thesis introduces the concept of sustainable development as a legal concept. The main idea is to see whether both investment treaty and trade tribunals can use it as an intellectual lens to interpret the non-discrimination standards in both regimes, aiming for their future convergence. The thesis traced the evolution of the concept, its scope and application. Flowing from the theme of the discussion, the main findings reached are that by employing the rules of the Vienna Convention on the Law of Treaties, the concept of sustainable development can serve as a suitable interpretive tool for international courts and tribunals.