The principle of mutual trust has become a structural principle of EU law that underpins many rules of primary law as well as secondary legislation both in the field of internal market and in that of the area, of freedom, security and justice. Several questions in relation to this principle have had to be settled by the Court of Justice, particularly, with regard to the risks that it can pose for the protection of, fundamental rights in the area of freedom, security and justice. In this regard, the Court of Justice adopted a ‘stone-by-stone approach’, by progressively specifying the limits framing the principle of mutual trust on the basis of the specific cases it had to handle. Building on recent the case law, this paper offers a critical, examination of the balance struck by the Court of Justice between the, principle of mutual trust and the protection of fundamental rights.