The paper explores the issue of national culture and tradition within the framework of the EU internal market. It presents a discourse on the legitimacy of European economic integration. The author derives from the motto »Europe united in diversity« and discusses the meaning of diversity in the field of internal market. The paper emphasises the importance of institutional analysis in EU market law and analyses constitutional relations between national and supranational levels of government in the internal market field. Legal practice in the internal market (the case-law of the EU Court and legislation) shows a pro-centralistic orientation, within which several aspects of national culture and tradition have been sacrificed. However, the Court and the EU legislator did not openly discuss different institutional alternatives; instead they were mostly referring to the benefits of the established rules for the majority of the European citizens. In so doing, they eroded national regulatory autonomy in the market field and many important aspects of national tradition and culture have been sacrificed for reasons of pursuing an ideal internal market (e.g. national food and drink laws (such as Italian pasta rules, German bier production), rules on working days (Sunday trading) and hours (e.g. Spanish siesta), metrical systems etc.). The European process of market law uniformity, however, is contestable when assessed in light of democratic legitimacy. In this regard the paper analyses the effects of the principle of subsidiarity on the institutional analysis in the field of EU internal market.