Norm contestation offers a powerful lens for understanding why enlargement has become so fraught with conflicts. Drawing on constructivist debates around norm diffusion, hybridisation, clusters, and illiberal resistance, this analysis relocates enlargement from a story of compliance to one of interpretation and struggle. EU norms do not simply travel; they are redefined as they encounter local beliefs, strategic interests, and rival normative orders. Contestation appears not as a malfunction, but as a constitutive part of how norms gain or lose clarity and legitimacy. Framing accession as a normative construction site reveals how Western Balkan and EU actors together co-create, modify, and challenge the foundations of the 'European edifice' at a moment of intensifying geopolitical rivalry.