CAT/C/63/4 51. Further, detention measures must be applied in pursuit of a legitimate purpose. In the context of immigration detention, a “legitimate purpose” is the same for asylum seekers and migrants as it is for anyone else: when someone presents a risk of absconding from future legal proceedings or administrative procedures or presents a danger to his or her own security or the security of the public. The irregular entry by asylum seekers and migrants should not in itself be criminalized. V. Reflections on the year under review A. Capacity of national preventive mechanisms to work effectively in a preventive manner and the “preventive package” 52. In the light of its experiences over the last year, the Subcommittee considers it appropriate to reiterate the importance of national preventive mechanisms having true functional independence and being able to work with a preventive spirit, identifying potential risks of torture and ill-treatment, highlighting gaps in human rights protection and making recommendations of a practical nature to address matters of concern. 53. The Subcommittee is increasingly aware that even if they have a legal mandate to do so, not all national preventive mechanisms feel able to gain access to all places where people are being or may be deprived of liberty; to all persons deprived of liberty and to all information relevant to the mandate; and to have the right to interview detainees confidentially. Not only must they have the legal mandate to do so, they need the independence to be able to decide to do so, the means to do so and the confidence that they will in practice be capable of doing so. 54. The Subcommittee is of the view that a national preventive mechanism should also be empowered and able to deliver the whole “preventive package”, including examining patterns of practices from which risks of torture may arise; advocacy, such as commenting on draft and implementing legislation; providing public education; undertaking capacitybuilding; and actively engaging with State authorities. The Subcommittee emphasizes that this requires sufficient resourcing; appropriate privileges and immunities; and access to the Subcommittee for advice and assistance. B. State party obligations 55. The Subcommittee reiterates the need for all States parties to understand the Optional Protocol and ensure that their obligations to the Subcommittee under the Optional Protocol are met. In that regard, it is fundamental that States parties do not, directly or indirectly, actively or otherwise, hinder the Subcommittee in fully carrying out its visiting mandate, in accordance with articles 12 and 14 of the Optional Protocol. That includes, inter alia, the obligation to provide the Subcommittee with all necessary information, including all the documentation that it requests, both prior to and during the visit; the obligation to ensure the Subcommittee has unhindered access to all places under its jurisdiction where people are or may be deprived of their liberty; the opportunity to have private interviews with persons deprived of their liberty and others, including but not limited to guards, officers and professional and managerial staff of the facilities being visited. The Subcommittee has set out those obligations on numerous occasions. It appreciates that it might be helpful for it to explain early and clearly the requirements of the Optional Protocol to those States about to be visited, during the preparatory phase, and it will ensure that this is done. C. Article 16 (4) of the Optional Protocol 56. If a State party refuses to cooperate with the Subcommittee or fails to provide an enabling environment within which the Subcommittee can fulfil its mandate in accordance 10