Limits of Integration through Mutual Trust in the EU

This paper analyses the principle of mutual trust as a methodological tool for EU legal integration. The principle of mutual trust is an ambitious creation of the CJEU. One can find its origins in the mutual recognition case-law of the Court. Very early in its internal market case-law, the ECJ referred to the principle of mutual recognition (Cassis de Dijon). Later, the concept spread to the mutual recognition of diplomas and court judgments. Thereby, when harmonization rules are lacking, the principle of mutual recognition should help to ensure “unity in diversity”. The principle of mutual trust – first of all legal trust between Member States – is in turn based on the mutual cultural and legal heritage of the Member States. The Court's audacious case-law has gradually transformed the mutual trust principle into an integration tool. But many recent events (e.g. sovereign debt crisis, migration crisis, COVID-19 and the rule of law crisis) show the limits of this integration method.