This thesis aims at addressing the problem of a potential dis-embedding of the EU administration from democratic institutions. For that purpose it explores the potential of a novel approach to EU constitutionalism, namely of European conflicts-law to ensure the democratic legitimacy of EU administrative governance of GMOs. The term administrative governance is being used as referring to a system of administrative action, in which EU administrative actors implement EU law in cooperation with national administrations, as well as with scientific and private experts. In order to analyse the functioning of this system governance is employed as analytical framework. This thesis shows that the conflicts-law approach constitutes a valuable constitutional framework. It helps to identify and better understand the legitimacy problems of EU administrative governance in the field of GMOs. The existent legal rules in this area can to a certain extent be reconceived as embodying conflicts-law mechanisms and ideas. This is most visible in their aim to procedurally organise cooperation between various actors within horizontal network structures of decision-making. However, the implementation of GMO rules in practice has considerably undermined the functioning of conflicts-law mechanisms. The analysis reveals problematic shifts of authority, which go beyond the system of shared responsibility envisaged by the EU legislator. Instead of administrative cooperation between national and supranational actors, hierarchy in the sense of central decision-making by the Commission dominates the process. Moreover, instead of shared responsibility between public authorities and the biotech industry, the applicant has become a powerful player of GMO regulation. This has to some extent also undermined the application of the precautionary principle in this area. This thesis concludes that attempts of EU law to constitutionalise administrative governance of GMOs in a legitimate way have not proven to be successful so far. Finally, this thesis also reveals certain limitations of the conflicts-law approach. It is suggested that conflicts-law at present should not be considered as a fully-fledged theory of European integration. Its strength lies in the ability to re-direct the discussion on democratic legitimacy of EU law, and to offer constitutional ideas for further elaboration of regulatory solutions. However, further conceptual clarifications seem necessary in order to make it operational in concrete cases of EU regulation.