In the area of core state policies, the European Union has sought to strengthen the legitimacy of integration by allowing for greater differentiation and by involving parliamentarians in the form of interparliamentary conferences. This study examines a possible trade-off between these two strategies. It tests the expectation that parliamentarians from countries that are partially or fully exempted from a policy area might not consider participation in interparliamentary conferences worthwhile – thus depriving EU institutions of the opportunity to transmit information about their policies to them directly rather than indirectly through parliamentary oversight procedures at the national level. The empirical analysis relies on comprehensive data on participation in interparliamentary conferences in the areas of Economic and Monetary Union, foreign and defence policy, and justice and security policy.
