The CGLPL then flagged the most restrictive practices in terms of freedoms which include such restraint methods as placement in a seclusion room and use of mechanical restraint instruments, voicing particular concern over the situation of detainees in crisis, who are systematically subjected to restraint methods. The CGLPL put forward recommendations aimed at improving the extent to which the United Nations Convention on the Rights of Persons with Disabilities is taken on board in mental health institutions, and implementation of its approach centred on human rights. The CGLPL also addressed afresh the issue of prison overcrowding, on which recommendations had been issued during the last UPR, focusing on alternative sentences and promoting reintegration. It reiterated that the issue could not be dealt with solely from the prison angle, and that simply building new prison places was not an effective solution. A fully-fledged public policy involving all of the stakeholders in the criminal justice chain needs to be rolled out, along with prison regulation mechanisms. The Nelson Mandela Rules After four years of consultation, the revision of all of the 1955 Standard Minimum Rules for the Treatment of Prisoners was adopted at the end of 2015 by the United Nations General Assembly, and renamed "the Nelson Mandela Rules". These now contain a more extensive section on the absolute prohibition of torture and other cruel, inhuman or degrading treatment or punishment. What is more, the importance and necessity of supervision of prisons is now recognised, along the lines of the Optional Protocol to the Convention against Torture and other Cruel, Inhuman or Degrading Treatment or Punishment (OPCAT): the Rules recommend setting up a twofold system for regular inspections of prisons, entailing internal or administrative inspections, and external inspections conducted by a body independent of the prison, such as the NPM or international organisations. In the context of promoting these Rules, the CGLPL first participated in a consultation of experts organised by the Justice Section of the United Nations Office on Drugs and Crime (UNODC), bringing together representatives of prison administrations of the OSCE's Atlantic pillar, as well as international associations and organisations. The CGLPL was the only NPM represented at this high-level meeting, which aimed at establishing a tool enabling States to assess the compliance of their national prison systems with the Nelson Mandela Rules, and thus facilitate their practical application at national level. It then shared its expertise at a regional meeting organised by the OSCE Office for Democratic Institutions and Human Rights (ODIHR), Penal Reform International and the UNODC in Warsaw. The experts examined the content of a practical guide to the Nelson Mandela Rules for the attention of prison administrations and their staff. Participation in these discussions informed efforts to take on board the revised standards at the CGLPL. In this context, thanks to the summer school organised by the Association for the Prevention of Torture and University of Bristol, the subject could be delved into in greater depth: its programme was drawn up in a bid to acquire technical knowledge on the main provisions of the Nelson Mandela Rules so as to inform supervisory missions, and issue sounder recommendations. Codification of international standards governing immigration detention The Council of Europe's European Committee on Legal Co-operation (CDCJ) has conducted a codifying exercise on a detailed set of immigration detention rules, based on international and regional standards. However, because immigration detention law is incomplete, the codifying exercise revealed a number of gaps: definition of places of detention, provision for vulnerable groups, disciplinary problems, etc. In order to overcome this difficulty, the writers have decided to transpose the European prison rules each time there is no corresponding standard. As such, the draft instrument involved applying to detained migrants the rules established for prisoners, thereby adopting a criminal justice approach to detention. 108