Following the entry into force of the Charter of Fundamental Rights in domestic legal order and the future adhesion of the European Union to the European Convention of Human Rights, it is necessary to clarify the relationship between the Court of Justice of European Union and the European Court of Human Rights and the contradictory obligations arising for national courts when they implement fundamental rights in domestic legal orders. In this context, this scientific monography examines the nature, purpose and effect of constitutional dialogues between the Court of Justice of the European Union, the European Court of Human Rights and domestic courts. The book analyses recent case-law of the Court of Justice and proposes to see the relationship between courts in Europe under the framework of a cooperative judicial dialogue, named “deference”, that is based on the autonomy and voluntary willingness of national courts to ask for guidelines from the Court of Justice when they are implementing EU law. The Court of Justice is also using the ‘deferent dialogue’ towards national courts. Constitutional courts sometimes do not send for a preliminary ruling while still following the Court’s precedents, thus avenues of ‘silent dialogues’ are also explored. The case-law where constitutional courts exercised their competence to indirectly review the validity of EU legislation in light of the protection of fundamental rights is discussed. Finally, the case-law of the Luxembourg Court is heavily citicized as it failed to ensure the necessary overall coherence of the European system of protection of fundamental rights. In conclusion, the European judicial system, unlike other federal systems, still needs to pay attention to ensure the effectiveness of the system of protection of human rights. Further, for judicial dialogues to function properly, both the Court of Justice and constitutional courts should show “deference” to each other’s sensitivities in light of the principle of loyal cooperation entrenched in the EU Treaties.