In this article it will be argued that the contribution of political theory to European studies is rather one-sided and could be enriched by broadening the spectrum. To make this clear, the first part of this article will offer an overview of the contribution of political theory to European integration studies up to the present day. In the second part, avenues for further research will be presented with special attention to the importance of theories of justice for the EU. In close connection to this program, the value of ideal theory will be highlighted as a means to think about the further development of the EU and to critically assess the present functioning of the EU.