As deprivation of liberty must conform to the principle of necessity and proportionality,[19] the Reception Directive of the European Union as well as its transposition into Greek foresees an exhaustive list of reasons under which asylum seekers can be detained:[20] In order to determine or verify his or her identity or nationality; In order to determine those elements on which the application for international protection is based which could not be obtained in the absence of detention, in particular when there is a risk of the applicant absconding; In order to decide, in the context of a procedure, on the applicant’s right to enter the territory; When a third country national is already detained and, subject to a return procedure, lodges an application for asylum merely in order to delay or frustrate the enforcement of the return decision; When protection of national security or public order so requires; Where the applicant should be transferred to another Member State under the Dublin Regulation and there is risk of the applicant absconding, in order to ensure proper implementation of the transfer procedure. Only after an individual assessment and only if it is considered imperative and no alternative measures can be applied, can an asylum seeker exceptionally be detained for one of the above reasons. However, there are serious doubts whether the Greek police, as the competent authority to impose detention, is conducting individual assessments and is taking into account the particular circumstances of each case.[21] Also, the correct application of certain detention grounds for asylum seekers is not given. For example, the excessive use and misuse of public order grounds for the detention of asylum seekers has been frequently reported in previous years,[22] detaining applicants without a proper assessment if they represent a sufficiently serious threat.[23] Asylum seekers can only be detained for as long as it is absolutely necessary and as long as the grounds for their detention are applicable. “Administrative procedures relevant to the grounds for detention set out in Article 8(3) shall be executed with due diligence. Delays in administrative procedures that cannot be attributed to the applicant shall not justify a continuation of detention.”[24] In Greece asylum seekers can be detained for an initial period of 50 days, which can be extended for another 50 days. The maximum time frame for an asylum seeker to be detained is 18 months.[27] Yet, the detention period in view of removal is not calculated in total time, meaning that the maximum time a third country national can be detained is 18 months while in the asylum procedure, plus an additional period of 18 months in view of removal.[26] Basic Principles & Legal Structures for the Detention of Third Country Nationals Any third country national considered to be staying illegally and who is subject to return procedures can under certain circumstances be detained. Third country national in this sense means, a person who is not yet or not any more an asylum seeker. Like the detention of asylum seekers, the deprivation of liberty of third country nationals is considered a serious interference with basic human rights and therefore only admissible under certain strictly regulated conditions. 11