This doctoral dissertation examines from a comparative perspective, the negotiation autonomy of Austrian Belgian and German federal executives in the Council of the European Union vis-à-vis their domestic parliaments. In particular, it aims at explaining to what extent, how and why regional and national parliamentary actors scrutinise EU decision-making processes, as well as the consequences on the negotiation autonomy of federal executives. This thesis presents original empirical data on four legislative decision-making processes (period 2009-2014) in the environmental policy field, a competence partly regionalised in Austria, Belgium and Germany. The study uses the Qualitative Comparative Analysis (QCA) method and assesses the impact these following five variables have on the negotiation autonomy of federal executives: (1) the preference homogeneity between federal executives and domestic parliaments, (2) the cohesion of the domestic parliamentary system, (3) the existence of an informational asymmetry in favour of federal executives, (4) the domestic salience of the EU decision-making process, and finally, (5) the impact from the implementing powers domestic actors own. Overall, this doctoral dissertation defends two main theoretical (and empirical) arguments. First, the dissertation shows that in federal Member States, the scrutiny of EU affairs conducted by regional parliaments do matter. It is the combined actions of national and regional parliaments (the parliamentary system) that explain the degree of negotiation autonomy for federal executives. Second, the study also demonstrates that a high level of activity from domestic parliaments does not directly translate into diminishing autonomy for the executive. These are crucial findings as most studies focusing on (sub)national parliaments and the European Union (EU) rest on the implicit assumption that strong and active parliaments in EU affairs lead to an improved accountability of the governments. Against this background, the results show that federal ...