INTRODUCTION Immigration Detention in Greece The introduction of the Schengen agreement, signed in 1985 but implemented as the Schengen Area in 1995, aimed to establish an area of free movement, particularly of people and goods.[1] However, to compensate for the abolishment of internal borders, an array of measures have been established to fortify the external borders of Europe and prevent third country nationals from entering.[2] The past three decades have therefore seen European Union (EU) Member States develop extensive legislative and administrative instruments to navigate the arrivals of people on the move, and order their removal if their stay is considered illegal. This, alongside the continued lack of harmonisation of the Common European Asylum System (CEAS), which enables governments to reform their own laws and practices, has seen immigration detention become institutionalised and normalised in EU Member States.[3] Return procedures and Pre-removal Detention Centres (PRDCs) facilitate the practice of detention, depriving third country nationals of their liberty in order to carry out their removal. Despite the fact that this should still remain the exception and a measure of last resort according to EU legislation, many EU States have resorted to detention as a de facto policy for irregular third country nationals. In Greece, the detention of third country nationals was enshrined in law in 2005,[4] and by 2010, Amnesty International[5] and Human Rights Watch[6] expressed severe concerns over the departure of detention practices from being used as a last resort, thus diverging from both law and human rights. The influx of arrivals in 2015 to European borders also significantly increased the use of administrative detention for third country nationals. This is particularly the case for external Member States, including Italy and Greece,[7] which are common entry points to the EU. In Greece, the number of third country nationals subject to detention rose from 3,000 in 2017, to 4,000 in 2019-2020, yet the number of formal deportations has been steadily declining since 2018. This raises doubts with regard to the necessity and proportionality of detention.[8] Furthermore, in 2021, the Greek Ombudsman particularly noted the increase in administrative detainees of Afghan nationality, and with the continued suspension of readmissions to Türkiye since March 2020, this additionally raises questions regarding the reasonable prospect of removal.[9] 8