Mutual trust in EU law : trust ‘in what’ and ‘between whom’?

Mutual trust is a fundamental principle of European Union (EU) law. It co-creates and justifies the autonomous nature of the EU legal order and operates as a vital component of its proper functioning. With reference to the reasoning used by the Court of Justice of the EU to justify the existence of mutual trust in EU law, the article identifies the general legal characteristics of this principle and examines the limits of its application. In this respect, two questions are analysed: rust is complex and limited by ensuring the actual implementation of values enshrined in article 2 of the Treaty on European Union. As a related normative claim, it argues that the principle should be applied in a way that cannot endanger or undermine any of these values. Subsequently, it examines between what subjects the principle applies, focusing on the Member States, EU institutions, and even non-EU countries. As the principle applies mutually between its subjects, the article suggests that these subjects should be bound by the object of trust to the same extent and assesses whether this requirement is fulfilled