The governance of the humanitarian dimension of migration is one of the most salient challenges for the EU and for European integration as a process. One core aspect of migration today rests on externalization policies, which aim at creating transnational governance structures geared at sharing the administration of the preventive containment of migration flows directed to Europe. These externalization policies feature predominantly the actorness of executive organs; they take place with informal acts, instead of formal legal instruments; they materialize more and more in practices of shared administration enabled by new technological and communication infrastructures. Informality of instruments and the operational dimension challenge traditional accountability mechanisms. Which is the most appropriate forum for ensuring accountability for the actions described above? The article defines different situations and scenarios and also sketches out different liability frameworks.