Why national parliamentarians join international organizations

It is customary to argue that international organizations (IOs) are very much dominated by national executives, with national parliaments wielding no or at best marginal influence. According to this accepted wisdom, there cannot be many reasons for national parliaments and their members to be active within IOs. However, we can observe a movement towards the parliamentarization of IOs, materialized in a growing number of parliamentary bodies with increasing competencies that accompany governmental actions and decisions. My paper wants to shed light on the underlying incentive for members of national parliaments (MPs) to engage in these international parliamentary assemblies (IPAs). Proceeding from the assumption that IPAs can enable parliamentarians to fulfil their representation and control function, I argue that (1) district level factors related to internationalization can explain why some MPs become members of IPAs, and (2) opposition parties can use the information generated in IPAs to control governmental activities in International Organizations. I test the claims with data of all parliamentarians of the recent legislative period of the German Bundestag and personal interviews with 10 IPA members. The results suggest that especially district incentives are positive predictors for membership in the different assemblies, whereas variance in membership can hardly be explained by party-level factors.