In the last two decades, post-communist states experienced a fascinating political journey, from using the rule of law concept in the most general way as an early signal of the coming constitutional and political transformation, to specifically (as EU Member States) addressing the problem of the supremacy of EU law and its effect on emerging national democracy and constitutional sovereignty. In other words, they moved from asking the question ‘which rule of law?’ to the question ‘the rule of which law?’

This move itself indicates the capacity of the rule of law, which is discussed in this article, to operate as a political ideal and a power technique at the same time. This duality of the rule of law operations will be outlined against the background of the process of European integration and its challenges to the traditional constitutional notions of sovereignty and legal unity. I shall argue that post-communist states initially had to embrace the substantive concept of the rule of law drawing on liberal and democratic values, which became a valid ticket for ‘The Return to Europe’ journey. However, the very process of European integration involved technical uses of law often challenging the substantive notion of the democratic rule of law and constitutionalism. The accession of post-communist states to the EU thus highlights the Union's more general problem and intrinsic tension between instrumental legitimacy by outcomes and substantive legitimacy by democratic procedures and values.