This paper discusses the precarious relationship between the principles of mutual trust and the
rule of law in the EU. It illustrates a tense interaction between the two as, although the principle of
mutual trust has become a tool to tackle rule-of-law failures in Member States, it long before that also created serious rule-of-law problems in the EU itself. However, it has not always possessed the effect and potential to enforce the rule of law and Article 2 TEU values in the Member States. The paper first shows the case-law developments necessary for the instrumentalisation of mutual trust for ruleof-law purposes. It then asks the question whether a lawfulness presumption is at all an adequate principle from a rule-of-law perspective, as such a presumption frustrates effective judicial controls claimed to be of the essence of the rule of law in the EU. As the case-law examples show, mutual-trust presumptions have already had severe rule-of-law ramifications in recent years by allowing, upholding and extra-territorialising alleged manifest errors and non-compliances in practice. Besides the more well-known sensitive areas of fundamental rights pertaining to asylum and criminal law, the paper showcases the more overlooked area of civil-justice case-law. The case-law analysed suggests that it is doubtful whether a lawfulness presumption is an adequate judicial principle from a rule-oflaw standpoint – if compliance presumptions are not receptive to actual facts on the ground for overruling the presumption, they also bring about serious rule-of-law and legality issues. Thus, although it facilitates inter-State co-operation, the effectiveness of EU law and everyday judicial practice, the newly acquired instrumental usage of mutual trust as a vehicle for enforcing Article 2 TEU values and
the rule of law in Member States might be questionable and susceptible to criticism.