A/HRC/12/22 page 6 10. The Covenant also contains rights and safeguards that must be guaranteed immediately. One example is the obligation on States to guarantee non-discrimination, including ensuring the equal rights of men and women in the enjoyment of economic, social and cultural rights. Moreover, a number of rights contained in the Covenant can clearly be implemented immediately, irrespective of the resource constraints of a State, including the right to join and form trade unions, protection against forced evictions, or the freedom indispensable for scientific research and creative activity.6 11. The Committee on Economic, Social and Cultural Rights defined the minimum core obligations of the Covenant, which are obligations considered to be of immediate effect to meet the minimum essential levels of each of the rights. Where any significant number of individuals are deprived of enjoying them, prima facie, States parties would be considered as failing to discharge their obligations under the Covenant.7 Minimum core obligations are generally determined by having regard to fundamental needs, particularly of the most vulnerable persons. The Committee holds the view that for a State to attribute failure to meet its minimum core obligations to a lack of resources, it must show that “every effort has been made to use all resources that are at its disposition in an effort to satisfy, as a matter of priority, those minimum obligations”.8 The Optional Protocol to the Covenant, adopted in December 2008 by the General Assembly, refers to the “reasonableness of the steps taken by the State party”.9 12. When allocating available resources to different programmes, due regard should be given to the core content of each right, with special focus on the requirements of “the vulnerable members of society”.10 In the words of the Committee, “even where the available resources are demonstrably inadequate, the obligation remains for a State party to strive to ensure the widest possible enjoyment of the relevant rights under the prevailing circumstances”.11 13. It should be noted that violations of economic, social and cultural rights can occur through the adoption of retrogressive measures that reduce the extent to which any right is already guaranteed.12 Every State is obliged to ensure for everyone under its jurisdiction access to the minimum essential rights, and there is a strong presumption that retrogressive measures taken in 6 See Committee on Economic, Social and Cultural Rights, general comment No. 7 (1997) on the right to adequate housing (art. 11 (1) of the Covenant): forced evictions, and A/HRC/4/18. 7 Committee on Economic, Social and Cultural Rights, general comment No. 3, para. 10. 8 Ibid. 9 Article 8, para. 4. 10 Committee on Economic, Social and Cultural Rights, general comment No. 3, para. 12. 11 Ibid., para. 11. 12 See footnote 4 above, Maastricht Guidelines on Violations of Economic, Social and Cultural Rights, para. 14.