26 INTERNATIONAL LEGAL PROTECTION OF HUMAN RIGHTS IN ARMED CONFLICT  The provisions of international human rights treaties: article 4 of the Optional Protocol to the Convention on the Rights of the Child on the involvement of children in armed conflict specifically imposes some degree of obligation on armed groups. The Committee on the Rights of the Child, in its 2001 concluding observations on the Democratic Republic of the Congo, alluded to the responsibility of armed groups and private companies for violations of the Convention on the Rights of the Child in the context of the armed conflict;28  The practice of United Nations organs: the Security Council has, on a number of occasions, called on all parties to a conflict, including non-State actors, to respect international humanitarian and human rights law. For example, in resolution 1564 (2004), it stressed in the preamble that “the Sudanese rebel groups […] must also take all necessary steps to respect international humanitarian law and human rights law”;  The practice of non-State actors: in 2005 the Communist Party of Nepal-Maoist issued a statement welcoming the establishment of a United Nations human rights field operation in Nepal, promising United Nations personnel full access to the areas it controlled and committing itself to respecting human rights standards. The Office of the United Nations High Commissioner for Human Rights (OHCHR) later determined that the Party had not respected human rights and had acted to limit some rights. In El Salvador, the Frente Farabundo Martí para la Liberación Nacional and the Government entered into the San José Agreement on Human Rights, co-signed by the United Nations Secretary-General. Moreover, as will be explained in the following chapter, gross violations of human rights and serious violations of humanitarian law could entail individual criminal responsibility, including for violations committed by members and leaders of non-State armed groups.   CRC/C/15/Add.153. 28