Jan Klabbers examines how membership of the European Union affect treaties concluded between the member and non-member states.

Jan Klabbers questions how membership of the European Union affects treaties concluded between the Union's member states and third states, both when it concerns treaties concluded before EU membership and treaties concluded after joining. Following a discussion of the public international law rules on treaty conflict, the author analyzes the case-law of the European Court of Justice and examines how such conflicts are approached in state practice.