Governing Critical Maritime Infrastructure in the European Union; Path-Dependent Transformation and Institutional Change

The subsidiarity paradox, in which formal affirmations of national prerogative coexist with factual EU-level centralisation, is a well-documented feature of European security governance. How this paradox unfolds in specific critical infrastructure sectors, however, remains insufficiently understood. This article asks how the EU’s governance of critical maritime infrastructure has transformed across three phases between 2014 and 2025 and to what extent the mechanisms of institutional change documented for crisis governance and the regulatory security state in adjacent sectors account for this trajectory. Drawing on a qualitative content analysis of 21 EU documents, it identifies three governance phases and five ideal-typical governance modes, and demonstrates that external shocks, most decisively the Nord Stream sabotage of 2022, opened windows of opportunity for institutional change. This change proceeded through layering and conversion instead of rupture and confirms the pattern of institutional syncretism observed in adjacent policy fields. The result is a stable coexistence of hierarchical and network-based governance modes whose functional differentiation reflects the jurisdictional reach of EU law. The article extends the meso-level analysis of EU crisis governance to critical maritime infrastructure and specifies the legal mechanism through which subsidiarity and centralisation coexist in this domain, namely the use of internal market competences under Article 114 TFEU to regulate substantively security-related matters. It further shows that lock-in effects channel rather than obstruct institutional change, offering a corrective to path dependency accounts that treat lock-ins primarily as barriers to reform.