A/HRC/23/46 be at the disposal of member States in order to secure borders and prevent arrivals, rather than a genuine life-saving tool. 45. Moreover, even when certain safeguards with regard to human rights at the border appear to be guaranteed in principle, the concern in relation to implementation remains, especially with regard to specific needs of vulnerable migrants and asylum seekers. For example, while the Stockholm Programme provides that the activities of Frontex and of the European Asylum Support Office (EASO) should be coordinated when it comes to the reception of migrants at the Union’s external borders, the Special Rapporteur notes that this is presently not the case. In Greece – while Frontex screens migrants at the border, in order to establish their nationality to facilitate their expulsion, EASO is not present , and the European Union does not assist member States with the screening of migrants at the border in order to identify protection needs. Similarly, in Italy, Frontex guest officers were permitted to interview migrant detainees in detention centres, without any supervision. The recent working arrangement between Frontex and EASO allows for the possibility of establishing common or mixed teams of border managemen t and asylum experts. This could be further explored as a way to mainstream effective and timely identification of persons with international protection needs in Frontex operations, provided that such mixed teams are subject to effective human rights monitoring and involve UNHCR. 46. Furthermore, as the Mediterranean is a busy sea, private vessels could potentially provide invaluable assistance to migrants in distress at sea. Border guards mentioned to the Special Rapporteur that boats in distress are often sighted by private vessels prior to getting into danger. However, the criminalization of migration has contributed to the reluctance of private vessels in assisting migrants in distress. In particular, known difficulties in disembarking migrants, the high costs associated with such intervention, and the lack of cooperation by States with private entities seeking to provide such humanitarian assistance, as well as the potential repercussions for private individuals, has resulted in the reluct ance of private vessels to take responsibility for boats in distress, thus compounding the risk of death at sea. 4. Detention as a tool in border control 47. At the outset, the Special Rapporteur recalls his doubt that detention is ever an effective deterrent for irregular migration, and that in order not to violate international human rights law, detention must be must be prescribed by law and necessary, reasonable and proportional to the objectives to be achieved.14 However, in the context of his country visits and his research, the Special Rapporteur has observed that, within the discourse of securitization of migration and border control, the systematic detention of irregular migrants has come to be viewed as a legitimate tool in the context of European Union migration management, despite the lack of any evidence that detention serves as a deterrent. Indeed, a notable increase in the use of immigration detention as a tool for European Union border control over the past 10 years corresponds to the development of European Union migration law in this area. In some senses, the harmonization of European Union law, and in particular the passing of the Return Directive, can be said to have institutionalized detention within the European Union as a viable tool in migration management. 48. It should of course be noted that, in fact, the Return Directive stipulates that detention should be a measure of last resort. Yet, in practice, few viable alternatives to detention appear to be explored by the European Union institutionally and by European Union member States individually. In the countries visited the Special Rapporteur 14 12 Report of the Special Rapporteur on the human rights of migrants, A/HRC/20/24.