  It obtains unequivocal guarantees that the persons concerned will not be subjected to ill-treatment; and Establishes a system to monitor their treatment after their return. 72. Importantly, the deporting State may incur responsibility where the authorities of the target country are ‘unable or unwilling’ to provide effective protection from ill treatment by non-State agents. 73. Due process safeguards must also be put in place to ensure that any person subject to return can challenge their return, including reliance on any diplomatic assurance and propose monitoring arrangements, before an independent and impartial tribunal. I. Monitoring and inspecting places of detention 74. Instruments such as the Optional Protocol to the UN Convention Against Torture (OPCAT) recognise that ‘regular inspection to places of detention, especially when carried out as part of a system of periodic visits, constitutes one of the most effective preventive measures against torture’.394 75. Such inspections should be regular, independent, whereby the inspectors are able to speak with detainees in private.395 OPCAT in particular requires States to establish their own independent monitoring body or bodies at the national level to monitor places of detention. J. Rendition 76. The UN High Commissioner for Human Rights has also expressed significant concerns about the use of unlawful rendition or the transfer of non-national suspected terrorists who are considered to pose a security risk to their countries of origin or third countries. 77. Transfer, in this context, is defined as the involuntary relocation of non-citizens across borders from the custody of one government to another, regardless of the procedure used and its basis in law, or lack thereof. Often, these transfers are carried out on the basis of assurances from receiving States that persons will not be tortured or ill-treated. 78. The High Commissioner for Human Rights has pointed out that cases have come to light that demonstrate that some of these transfers are taking place outside the law, in the absence of procedural safeguards such as due process protection and judicial oversight. Persons subject to such transfers often have no ability to challenge the legality of their transfer or the reliability of the 394 Special Rapporteur on Torture, E/CN.4/1995/34, para 926. See OPCAT, also European Convention for the Prevention of Torture; Human Rights Committee, Japan, A/54/40 (vol. I), p. 67. 395 79