The Development of the Rule of Law in the European Tradition. This research investigates the historical evolution and conceptual foundations of the “rule of law” within the European tradition, with a particular focus on its role in shaping the legitimacy and institutional architecture of the European Union. While the rule of law has long been regarded as a cornerstone of European integration—once termed a “community of law”—its invocation in recent political crises reveals inconsistencies and contradictions. The research explores how this principle has been applied to both condemn judicial overreach in Hungary and Poland, and justify secessionist movements in Spain, while simultaneously being invoked to oppose parliamentary amnesty measures. These paradoxes highlight the urgent need to clarify the conceptual origins and material underpinnings of the “rule of law”. Our central hypothesis is that the rule of law emerged in contexts where ruling elites, though strong enough to build state institutions, were too weak to dominate unilaterally—forcing them to negotiate with competing social actors. This “principle of weakness” shaped liberal constitutional regimes by promoting legal limits on power. Drawing on the works of Hayek, North, Weingast, Acemoglu, and others, the research traces the rule of law’s development from early modern England and Prussia, through interwar Central Europe, to its present form in European Union institutions. It also examines pre-modern proto-constitutional experiments in Catalonia, Flanders, and Northern Italy. Employing a historical and interdisciplinary methodology, the study combines bibliographic analysis with empirical insights from legal, political, and economic history. The aim is to elucidate how socio-economic conditions gave rise to legal structures that limit state power, and to assess the European Union’s reliance on legal legitimacy in the absence of a fully democratic foundation. The research aspires to contribute to both academic debate and public discourse on the rule of law in Europe today.