Executive Summary This policy paper focuses on the legality of and terms of detention in regards to migration in Europe. The analysis is mainly focused on the legal instruments of the Council of Europe, the European Union, and the Greek domestic system. The Council of Europe (CoE) passed several resolutions to improve the detention facilities and their conditions among its Member States. The CoE guarantees certain rights to asylum seekers and irregular migrants based on the European Convention on Human Rights. The CoE passed Resolution 1707 as a general legal framework to harmonize when detention of asylum seekers and irregular migrants can be justified, the minimum standards and safeguards that detention centers need to satisfy, and alternative to detentions that member States should take. The CoE, also, focused two resolutions on its Mediterranean member States, particularly Greece. The CoE discussed objectives that Greece’s domestic detention policies should meet in order to be in compliance with the CoE’s standards. EU legal instruments establish that detention pursuant to migration occurs by a confinement to a particular place and deprivation of movement and liberty. Individuals may not be detained for the sole reason of seeking international protection or asylum. Detention can only be made on specific grounds and detainees must be held under certain conditions. The EU establishes certain guarantees including legal access, humane treatment, review of detention, etc. Review of the detention’s legality and justification must be done judicially or by administrative agencies. Further, review should be done automatically by the competent authorities (ex officio) at reasonable intervals or requested by the detainee. Detainees may not be held in ordinary prisons, but instead must be kept in specialized facilities.