The transition into the new millennium was characterized by a comprehensive opening of national borders worldwide, particularly in Europe. However, this also led to a significant increase in cross-border forms of organized crime and terrorism. In response, numerous new and highly specific forms of cross-border law enforcement have been established, particularly within the framework of the European Union, the Council of Europe, and the United Nations. Since law enforcement measures typically interfere with the individual rights of persons, the author addresses the fundamental question of whether and to what extent cross-border cooperation in criminal matters is subject to the same fundamental and human rights standards that apply to purely domestic criminal proceedings. To this end, the various forms of cross-border cooperation must first be examined.