The Common Foreign and Security Policy (CFSP) of the European Union (EU) has often been characterised by legal scholars as an intergovernmental ‘pillar’ within the constitutional structure of the EU, distinct from the type of law and legal processes common to other dimensions of the European integration process. The perceived limitations caused by the intergovernmental nature of the CFSP have contributed to the widespread view that it is largely ineffective in meeting its goals. This thesis analyses the CFSP by characterising it as a system of governance. Building on the language and meanings of ‘governance’, an institutional constructivist framework of legal analysis is developed. Using this framework helps to show that characterising the CFSP in this way demonstrates how its (legal) effects go beyond the instruments provided for in the Treaty on European Union. The CFSP as a system of governance can be seen to influence other Union-level instruments, tools and policies in which the EU’s foreign policy goals are pursued. The case is made that the CFSP can be understood as an integral part of the constitutional order of the EU and legal analysis need not be limited to the competences and instruments found in the Treaty. The thesis uses the Euro-Mediterranean Partnership (EuroMed) to demonstrate how the EU’s foreign policy goals are pursued. Although EuroMed was not formally created by a CFSP instrument, analysis of its institutional framework and operation shows that it bears close affinity with the CFSP goals, both globally and towards the Mediterranean. EuroMed can also be seen as a system of governance, in which the EU institutions act as strong, central actors which enable foreign policy goals to be pursued within an institutionalised framework. As a policy area within EuroMed, the broad issues of migration are examined against the background of growing EU competence in migration law and policy. The analysis demonstrates that migration issues have come to the forefront in EuroMed, which is increasingly used as a means by which foreign policy and security goals can be pursued by the EU under the guise of a ‘partnership’ with Mediterranean states. Applying the institutional constructivist framework of legal analysis to the CFSP shows that, as a system of governance, it has strong effects on other policy-making spheres within the EU, and these effects can justifiably be termed as ‘legal’. As such, the CFSP should therefore not be regarded as a policy which is limited in its usefulness but one which can be seen to fulfil its goals through a wider set of means than previously thought.