The Transitivity of Trust in the EU Judicial System: An Engine of Integration and a Source of Fragility

This paper examines the critical role of transitivity of judicial trust in underpinning and operationalising the European Union's multilevel judicial system. The EU legal order is founded upon the structural principle of mutual trust between Member States, which functions as a core transitive presumption. The fundamental premise of mutual recognition in EU law, exemplified by tools like the European Arrest Warrant, is the default presumption that Member State courts trust the judicial system of another Member State to, for example, be compliant with fundamental rights and EU law. However, persistent challenges to this presumption have necessitated that this mutual trust be mediated by the Court of Justice of the European Union (CJEU) via the preliminary reference procedure. When the foundation of trust is questioned, the CJEU intervenes to provide the authoritative interpretation. This ruling either reaffirms and restores the national judges' trust in each other or diminishes it, with corresponding consequences for the overall confidence in the CJEU itself. While this transitive judicial trust is the indispensable engine of judicial cooperation and integration, it is perpetually fragile in certain situations. The paper explores the functioning of this transitivity mechanism and its relevance for the trust and distrust between judges and its relevance for legal integration.