on violence against women, its causes and consequences; and on extrajudicial, summary or arbitrary executions; the Special Representative of the Secretary-General on human rights defenders; and the Working Groups on enforced or involuntary disappearances and on arbitrary detention. 78. The third type of monitoring is through peacekeeping and human rights field operations. Recently, the inclusion of human rights aspects in the mandates of United Nations peacekeeping operations has increased dramatically. The assignment of various human rights functions to the international personnel involved in their implementation has included monitoring the human rights situation and reporting on it. Extensive human rights mandates were assigned to the United Nations Observer Mission in El Salvador, the United Nations Transitional Authority in Cambodia, the United Nations Mission for the Verification of Human Rights in Guatemala, the International Civilian Mission in Haiti, the United Nations Mission in Bosnia and Herzegovina, the United Nations Transitional Administration in East Timor, the United Nations Interim Administration Mission in Kosovo and other such operations. 79. In addition, the United Nations High Commissioner for Human Rights has established human rights field presences with monitoring mandates in several countries, among them Colombia and the Democratic Republic of the Congo. The field presence in the Democratic Republic of the Congo is mandated to, among other things, monitor the human rights situation throughout the country, give advice to governmental and non-governmental organizations on international human rights standards and provide information on individual cases of human rights violations that may require urgent action by the country special rapporteur and/or the thematic mechanisms. Furthermore, requests for technical cooperation programmes aimed at establishing or strengthening national human rights capacities or national human rights infrastructures are becoming a dynamic part of OHCHR’s work in the field. 7. How are human rights enforced? 80. International human rights law obliges States to take all necessary measures to give force to the standards contained in treaties and customary principles. This means, inter alia, ensuring redress for victims, prosecuting offenders, preventing abuses and combating impunity. Thus, in the first instance, it is individual States themselves which must act to enforce the standards, principally through their domestic legal systems. Where they cannot or do not act, or will not prosecute, States may be compelled, in certain circumstances, to extradite, transfer or surrender an alleged offender for prosecution elsewhere. Some treaties, such as the Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment, expressly require States parties to try or extradite offenders. 81. At the international level, in the 1990s, in the wake of genocide and crimes against humanity in Rwanda and the former Yugoslavia, ad hoc tribunals were established by the United Nations Security Council to bring to justice persons responsible for serious abuses in those countries. Subsequently, as the decade and the 34