How to Serve Two Masters: Conflicting Treaty Obligations in Cases of Dual Membership of NATO and the European Union

Since the establishment of NATO and the EU, the memberships of both these international organisations and associated territorial overlap has substantially increased. This thesis examines how dual NATO/EU Member States resolve conflicts arising from their obligations stemming from being members of both NATO and the EU at the same time. 

Being a dual Member State of different international organisations inevitably creates the possibility that the treaty obligations towards both these international organisations—and their Member States—are at odds. If a dual Member State acts in compliance with one treaty, this may, at the same time, result in a violation of the other treaty. A few cases regarding conflicting treaty obligations have been litigated before the Court of Justice of the European Union (CJEU). Nonetheless, this dissertation finds that while the respective conflict clauses in the NATO and EU treaties provide for a legal solution to these conflicts, a final resolution is mostly achieved through negotiations, rather than by court decision.