E/C.12/2017/1 prescriptions to the States parties with respect to the economic, social and cultural rights of refugees. However, those prescriptions leave in practice a broad margin of appreciation to States. The Covenant should be seen as complementing the Convention. 4. In the Covenant it is made clear that the rights recognized in it can only be progressively realized, to the maximum available resources of each State party (see art. 2 (1)). However, this does not mean that States parties may infinitely postpone taking action in order to secure the rights of individuals under their jurisdiction. In addition, the Covenant imposes a number of obligations of immediate effect. Such obligations apply even for the benefit of individuals who are part of a large group of refugees or migrants suddenly falling under the jurisdiction of the States concerned. Prohibition of discrimination on grounds of nationality or legal status 5. Under the Covenant, the requirement to guarantee all rights without discrimination imposes an immediate obligation on States parties. 3 Each State is left a certain margin of appreciation to decide which measures it should adopt to progressively realize the rights under the Covenant, provided such steps are deliberate, concrete and targeted as clearly as possible towards meeting the obligations recognized in the Covenant.4 Whatever measures it does adopt should, however, not lead to discrimination. Any distinction, exclusion, restriction or preference, or other differential treatment on grounds of nationality or legal status, should therefore be in accordance with the law, pursue a legitimate aim and remain proportionate to the aim pursued. A difference in treatment that does not satisfy such conditions should be seen as unlawful discrimination prohibited under article 2 (2) of the Covenant. In addition, article 3 of the Covenant requires States parties to ensure the equal right of men and women to the enjoyment of the Covenant rights. In accordance with the Committee’s general comment No. 20 (2009) on non-discrimination in economic, social and cultural rights, a lack of available resources cannot be considered as an objective and reasonable justification for difference in treatment “unless every effort has been made to use all resources that are at the State party’s disposition in an effort to address and eliminate the discrimination, as a matter of priority” (para. 13). 6. The Committee has made it clear that protection from discrimination cannot be made conditional upon an individual having a regular status in the host country. In its general comment No. 20, it emphasized, for instance, that since “the ground of nationality should not bar access to Covenant rights, … all children within a State, including those with an undocumented status, have a right to receive education and access to adequate food and affordable health care” (para. 30) and that (in addition to the right to self-employment, which is guaranteed to all refugees under the Convention relating to the Status of Refugees) any difference in treatment in access to employment would require justification in accordance with the criteria set out in paragraph 5 above. 5 The Committee notes in this regard that access to education and to employment are important channels for integration within the host country and will reduce the dependence of refugees or migrants on public support or private charity. 7. Consistent with the requirement of non-discrimination, States parties should pay specific attention to the practical obstacles that certain groups of the population may encounter in the enjoyment of their rights under the Covenant. Due to their precarious situation, asylum seekers and undocumented migrants are at particular risk of facing discrimination in the enjoyment of Covenant rights. 6 8. Article 2 (3) of the Covenant establishes one limited exception to the principle of non-discrimination on grounds of nationality in the enjoyment of the rights of the Covenant. This provision states that: “Developing countries, with due regard to human rights and their national economy, may determine to what extent they would guarantee the economic rights recognized in the present Covenant to non-nationals.” That exception only applies to 3 4 5 6 2 See the Committee’s general comment No. 3 (1990) on the nature of States parties’ obligations, para. 5. Ibid., para. 2. See also general comment No. 18 (2005) on the right to work, para. 31. See, for example, general comment No. 15 (2002) on the right to water, para. 16.