Borders are a constitutive feature of states. Political agency would, therefore, come into conflict with a practice of open borders. This is equally true for the dynamics of unleashed global financial and commodity markets as well as for a global labour market. An unregulated mobility of capital, goods, and people would erode the agency of states and diminish politics to a mere location factor. In the following, I argue in favor of the legitimacy of (state) borders and political control over migratory movements, however, not from a communitarian or even nationalist perspective, but from a cosmopolitan one. Political cosmopolitanism differs from sociological, economic, or cultural variants with regard to the role of politics. While other kinds of cosmopolitanism generally understand globalisation as weakening the agency of states, political cosmopolitanism strives for the establishment of a global institutional order, which allows for democratically legitimised political agency beyond the nation-state. The question is what institutional governance of migration is legitimate in a cosmopolitan framework. The following text discusses the political theory (part 1) and some preliminary philosophical-ethical aspects (part 2) of this topic.