In a recent request for a preliminary ruling, the Grondwettelijk Hof raised legal concerns to the CJEU as to whether Art 8ab para 5 Mutual Assistance Directive (DAC 6) is compatible with the Charter of Fundamental Rights. According to Art 8ab para 5 DAC 6, intermediaries who have been exempted from the reporting obligations by member states due to “legal professional privilege” (professional secrecy) must notify any other intermediary (in case there is one) about their reporting obligations. The Belgian Constitutional Court considers this to be an infringement of the professional secrecy of legal advisors and thus a possible violation of Art 7 and 47 of the Charter of Fundamental Rights. The professional secrecy of legal advisors is a cornerstone of their activity and a fundamental basis for a functioning rule of law. Mario Riedl analyzes the professional secrecy under EU law and, based on this, the underlying request for a preliminary ruling in light of Art 7 and 47 of the Charter of Fundamental Rights.