EU competition policy: Article 82 EC and the notion of substantial part of the common market

EU competition policy acts as an important buttress to the Single European Market, with Article 82 EC specifically prohibiting the abuse of a dominant position in the common market or a substantial part of it. Therefore the substantial part notion acts as a boundary or subsidiarity test, determining whether the alleged abuse falls under Article 82 or member state law. This paper contends that two different and potentially competing substantial part tests have been legally sanctioned, namely the territorial test and the economic relativism approach. It further reveals that court rulings have been instrumental in determining not only how the two tests are to be applied in practice but also their respective usage pattern.