National Parliamentary Coordination after Lisbon: A Network Approach

The Treaty of Lisbon strengthens the role of national parliaments as a collective veto player in the European Union by introducing an “early warning system" (EWS): any parliamentary chamber can object to legislative proposals, but a veto only becomes effective if a certain share of parliaments becomes involved. The possibility for individual chambers to state a reasoned opinion leads to two interrelated research questions: first, what factors guide individual parliamentary participation in the veto process -more specifically, which attributes of parliaments determine their individual veto actions? Second, how can we explain veto success, i. e., what proposal attributes and network effects cause more than one chamber to gather around a given proposal? The main theoretical contribution of the paper is the development of an argument that goes beyond individual institutional and partisan attributes of for explaining participation in the EWS. We rather argue that chambers' similarities of characteristics, especially similarity on the partisan dimension, matter for explaining why certain chambers engage in joint legislative activity. EWS actions essentially constitute a network because they are triggered by relational, rather than individual, incentives. Our relational claim is that chamber similarity breeds joint action and thus homophily explains legislative coordination among parliaments. To substantiate this claim, we conduct a quantitative analysis of all EWS activity of European parliamentary chambers from 2010 to 2014. We conceptualize parliamentary activity (and thus veto success following from this activity) as a two-mode network of chambers (vertex mode 1), proposals (vertex mode 2) and reasoned opinions of the chambers on these proposals (the edges in the two-mode network). This allows us to break new ground by analyzing the complex dependencies among national parliaments using bipartite exponential random graph models (ERGM). Note: co-authored with Philip Leifeld (philip.leifeld@uni-konstanz.de), co-author function in online mask did not work!