A/HRC/7/12 page 17 that the individual is unlikely to appear for an examination or a hearing, or where the officer is not satisfied about the identity of the person. Some anti-terrorism legislation allows for the detention of migrants on the basis of vague, unspecified allegations of threats to national security. The high degree of discretion and the broad power to detain accorded to immigration and other law enforcement officials, often coupled with a lack of adequate training, can give rise to abuses and to human rights violations. The failure to provide legal criteria can result in de facto discriminatory patterns of arrest and return of irregular migrants. 49. Moreover, there have been reports of searches that target the removal of migrants living in a host country. In some cases States have resorted to police “raids” on private homes in migrants’ neighbourhoods, arresting and detaining all residents who cannot show documents of legal residence, leading to separation of children from their arrested parents, including children born in such countries. All cases of expulsion should be decided upon on an individual basis and States should ensure that no collective expulsions take place.36 50. With such diversity in national policy and law governing detention and expulsion, it is important that irregular migration be seen as an administrative offence and irregular migrants processed on an individual basis. Where possible, detention should be used only as a last resort and in general irregular migrants should not be treated as criminals. The often erratic and unlawful detention of migrants is contributing to the broader phenomenon of the criminalization of irregular migration. 3. Smuggling and trafficking 51. The Special Rapporteur observes the continued abuse of irregular migrants who are involved, whether deliberately or inadvertently, in smuggling and trafficking operations. Over time the process of human trade has become more complex, whereby smugglers and traffickers may use a combination of deceptive, clandestine, or even legal modes of migration, switching strategies at different stages of the journey, and involving both legitimate and illicit actors at the governmental and non-governmental levels (inter alia, border officials, intermediaries, recruitment agencies, police officers, tourist agents, transport entrepreneurs and airline employees).37 The facilitation of cross-border movements has increased to such an extent that the networks rely on many players who may not be actively and knowingly participating in smuggling or trafficking activities as such. There is a concern that, in the process of preventing the proliferation of such networks and intercepting those involved, irregular migrants may not receive adequate protection. 36 The prohibition on the collective expulsion of non-nationals is arguably a recognized principle of international customary law. Indeed, the International Convention on the Protection of the Rights of All Migrant Workers and Members of Their Families is the most protective instrument for irregular migrants in international human rights law and affords additional rights, such as elaborate individualized protection against expulsion, which is limited to lawfully resident migrants in other instruments, such as ICCPR. See ICMW, article 22, and ICCPR, article 13, and the discussion in Cholewinski, et al., pp. 10-14. 37 Lee, pp. 2-3.