The protection of fundamental rights in the field of transnational criminal inquiries is of great delicateness in the current tangled web of domestic and international legal sources. Due to this complex scenario, this research has been carried out from a four-level perspective. The first part provides a critical analysis of the multilevel systems of protecting fundamental rights from the perspective of supranational and constitutional case law, and in the field of international and organized crime. The second part focuses on EU judicial cooperation in three main fields: financial and serious...