From being considered an international organization, a constitutional classification of the EU is today much more difficult, its function and federal structure being unprecedented in the world. With the division of competences, or the division of power to put it differently, between the EU and its Member States, the EU acts externally, internationally, often by concluding so-called "mixed agreements". This is a type of legal instrument whereby the EU and its Member States individually, on their own, express a willingness to be jointly bound by an agreement with one or more third parties. By coming together and jointly assuming the obligations and commitments of the agreement, the EU and its Member States can act as a single entity where the international agreement requires it. Thus, neither the EU nor the Member States could conclude the agreement in question on their own. Examples of these mixed agreements include the agreement concluded with the World Trade Organization (WTO), the UN Convention on the Law of the Sea and a number of trade agreements with countries in, for example, Africa. The purpose of my future research at Harvard Law School is to build on previous research and study mixed agreements in order to contribute to a clearer legal structure for these agreements. The research will largely be of a comparative nature, where the US and its federal structure will be contrasted with the federalism chosen by the EU and its member states.