A/73/207 resulting in widespread impunity for violations (A/HRC/34/54, para. 47, and A/HRC/28/68, para. 52). Under international law, however, States cannot absolve themselves of their responsibility for torture and ill-treatment carried out on their behalf, under their direction or control, at their instigation or with their consent or acquiescence. States are obliged to take effective measures with a view to prohibiting and preventing torture and ill-treatment in all such circumstances and providing redress to the victims. 16 (b) Extraordinary renditions 53. A particularly deplorable practice that has proliferated in the context of counter terrorism involves transferring detainees without due process to another country or territory for interrogation under torture and ill-treatment. Many States have facilitated such “extraordinary renditions”, including by allowing the use of their airspace and airports, or by hosting “black sites” where torture and ill-treatment occurred (A/HRC/13/42). Although the practice of renditions seems to have subsided significantly in recent years, the transparency, accountability, redress and reparations offered in respect of past practices remain grossly inadequate, with responsible officials being shielded from prosecution and investigations being plagued by a lack of independence, political will and other obstacles, thereby seriously undermining the prohibition of torture and ill-treatment. (c) Arrival prevention, readmission agreements and diplomatic assurances 54. In the context of migration, States increasingly conclude cooperation agreements with other States or non-State actors aiming to circumvent the prohibition of refoulement through the externalization of borders and procedures, or through extraterritorial “pushback” and “pullback” operations. In particular, “pullbacks” are designed to physically prevent migrants from leaving a (retaining) State or territory, or to forcibly return them there, before they can reach the jurisdiction of their destination State. In addition to their direct impact on the rights and safety of migrants, such practices have also facilitated the almost uncontrolled spread of abuse by a wide variety of individuals, including corrupt State officials and organized criminals. It must be reiterated that any participation in, or instigation and support of, such operations may give rise to complicity in, or joint responsibility for, the resulting human rights violations, including torture and ill-treatment (A/HRC/37/50, paras. 8 and 59). 55. Many States also conclude readmission agreements with other States, by which migrants are expelled without an individualized risk assessment to States that have been found to be “safe” on the basis of generalized criteria. This practice is incompatible with the procedural requirements of the prohibition of refoulement and may well amount to collective expulsion (A/HRC/37/50, para. 46). 56. Lastly, there is a widespread State practice of expulsions carried out based on diplomatic assurances by the receiving State that the person in question will not be subjected to torture or ill-treatment. In practice, diplomatic assurances are sought from States that are reasonably believed to practice torture and ill-treatment and the sending State generally lacks genuine interest in discovering subsequent non compliance by the receiving State. Even in conjunction with post -return monitoring mechanisms, therefore, diplomatic assurances are inherently incapable of providing sufficient protection against such abuse. The practice also expresses a disturbing complacency and acquiescence by the sending State with regard to merely selective __________________ 16 18-12051 Committee against Torture, general comment No. 2, para. 15. 15/23