Deportation gaps are presented by EU policy makers as a challenge to EU legality and, more generally, as an existential challenge to state sovereignty. On the other hand, non-deportability is generally viewed as a victory for migrants’ rights (and for good reasons). However, successfully resisting deportation does not necessarily come with a residence permit attached, and migrants might simply become non-removable, unable and/or unwilling to return to their countries of origin, but unable to access lawful residence. This thesis attempts to provide, primarily, a critical diagnosis of non-removability at the EU level, rather than a solution to it. In a context where deportation is increasingly normalised, both legally and politically, the present thesis inquires: why are EU Member States unable to deport as much as they claim to strive for? What are the consequences for those who stay without a valid residence permit? To answer these questions, this thesis proceeds as follows: First, this thesis situates the issue within its theoretical and legal framework. In doing so, it zooms in on migration control and non-deportability scholarship, lays out the applicable legal framework under the EU Return Directive, and problematises non-removability from a conceptual, normative, human rights and EU law perspective. Secondly, this thesis provides a comprehensive analysis of the European and EU processes that manufacture non-removability. To do so, it focuses on situations where legal claims to non-removal are not followed by lawful residence. This is found to take place when states’ non-refoulement obligations under European Human Rights Law are not followed by international protection under EU law, or when supranational claims to social membership are enough to resist expulsion but not to obtain a residence permit. Moreover, this thesis analyses ‘practical’ obstacles to deportation in light of EU readmission policies – and the ways in which they fail. Thirdly, this thesis inquires into the legal status of non-removable persons and identifies a threefold categorisation of non-removable migrants under EU law. The thesis concludes with a reflection on desirable legal and policy responses to non-removability and possible avenues for further research.