The case study research reported in Chapters 3, 4 and 5 follows a multiple case study design, 1 where the subject of analysis is the EU agency as defined earlier. The case studies provide an in-depth analysis and illustration of the international cooperation framework and practice of specific agencies, and assess this in light of the parameters laid down in the general legal-analytical framework of this study. In line with the queries of this study, all three case studies address the following common aspects: the legal nature of the international cooperation instruments of the selected EU agencies; their legal status on the international plane; and the compatibility of their international dimension with the EU constitutional framework, in particular the principle of institutional balance and the Meroni doctrine.