Limitations on article 13 42. The Committee wishes to emphasize that the Covenant’s limitations clause, article 4, is primarily intended to be protective of the rights of individuals rather than permissive of the imposition of limitations by the State. Consequently, a State party which closes a university or other educational institution on grounds such as national security or the preservation of public order has the burden of justifying such a serious measure in relation to each of the elements identified in article 4. 2. States parties’ obligations and violations General legal obligations 43. While the Covenant provides for progressive realization and acknowledges the constraints due to the limits of available resources, it also imposes on States parties various obligations which are of immediate effect. 19 States parties have immediate obligations in relation to the right to education, such as the “guarantee” that the right “will be exercised without discrimination of any kind” (art. 2 (2)) and the obligation “to take steps” (art. 2 (1)) towards the full realization of article 13. 20 Such steps must be “deliberate, concrete and targeted” towards the full realization of the right to education. 44. The realization of the right to education over time, that is “progressively”, should not be interpreted as depriving States parties’ obligations of all meaningful content. Progressive realization means that States parties have a specific and continuing obligation “to move as expeditiously and effectively as possible” towards the full realization of article 13. 21 45. There is a strong presumption of impermissibility of any retrogressive measures taken in relation to the right to education, as well as other rights enunciated in the Covenant. If any deliberately retrogressive measures are taken, the State party has the burden of proving that they have been introduced after the most careful consideration of all alternatives and that they are fully justified by reference to the totality of the rights provided for in the Covenant and in the context of the full use of the State party’s maximum available resources. 22 46. The right to education, like all human rights, imposes three types or levels of obligations on States parties: the obligations to respect, protect and fulfil. In turn, the obligation to fulfil incorporates both an obligation to facilitate and an obligation to provide. 19 See the Committee’s general comment No. 3, paragraph 1. 20 See the Committee’s general comment No. 3, paragraph 2. 21 See the Committee’s general comment No. 3, paragraph 9. 22 See the Committee’s general comment No. 3, paragraph 9.