CAT/C/63/4 the Subcommittee or by its work are significantly slower than was previously possible, when the working groups were able to work separately. 43. At the thirty-second session of the Subcommittee, the secretariat submitted a compilation of all the working methods of the Subcommittee in a consolidated document. The working group on procedural issues began considering the compilation and continued its consideration at the thirty-third session. However, due to a lack of meeting time and of available interpretation for the working groups, this work is being continued only informally and in parallel with the other urgent tasks of the working group. This approach will continue to be taken until additional meeting time and proper interpretation resources are allocated to the Subcommittee. This thus delays further the exercise to update the methods of work. 44. The working group on the health aspects of torture prevention has made significant progress in developing a checklist for national preventive mechanisms, which is aimed at providing an overview of relevant health-related issues that may be useful for mechanisms during visits to places of detention. The working group also continued working on the medical resource tool, a compilation of Subcommittee recommendations on health-related issues, based on reports of the Subcommittee following its visits. 45. The working group on the Special Fund has assisted those responsible for the review of applications to the Special Fund and with the promotion of the Special Fund, as recorded previously in the present report. 3. Regional teams 46. The regional teams and the respective country rapporteurs continue to engage with national preventive mechanisms. While the issues to be addressed and the manner in which they are to be addressed will vary from country to country, meetings of heads of regional teams during Subcommittee sessions ensure the application of a common objective yardstick, as does full plenary oversight. B. Issues of note 47. In exercising its mandate to visit places of detention, the Subcommittee has observed an increase in the practice of detaining migrants as a matter of routine, rather than as an exceptional measure of last resort. 48. The Subcommittee has observed that migrants in detention often do not enjoy their full legal rights to review and to due process, sometimes owing to a lack of access to legal counsel or interpretation services. The Subcommittee also believes that immigration detainees should be entitled, from the outset of their detention, to medical assistance and all due process guarantees. Detention exposes a group of persons who already find themselves in a particularly vulnerable situation at risk of becoming the targets of torture and illtreatment. While any person who is detained is vulnerable or at risk, some detainees are in situations of particular vulnerability, which is why, in order to address their special needs, the authorities have to take special measures. Among the most vulnerable are children, women, persons with a mental or physical disability, trafficked persons, victims of torture and trauma, stateless persons and lesbian, gay, transgender, bisexual and intersex persons. 49. International law stipulates that restrictions on liberty and the detention of migrants is to be exceptional and in response to a genuine legitimate purpose (for example, in order to protect public order, public health or national security, narrowly understood), and are both legal, non-arbitrary and respectful of human rights and dignity. 50. The requirement of legality necessitates that any restriction, including detention, may be imposed only on the grounds prescribed by law and in accordance with procedures authorized by law. Any form of immigration detention that is not specifically provided for in domestic law, or not carried out in accordance with domestic law, would therefore necessarily be unlawful and impermissible. Of course, domestic law must also be in accordance with international legal obligations. 9