However, accessibility of itself, is not always sufficient to ensure the rights of persons with disabilities; reasonable accommodation is also necessary. 53. According to the CRPD, reasonable accommodation means necessary and appropriate modifications and adjustments that do not impose a disproportionate or undue burden, where needed in a particular case, to ensure to persons with disabilities the enjoyment or exercise, on an equal basis with others, of all human rights and fundamental freedoms.67 Thus, whereas accessibility, in general terms, is aimed at ensuring access to the majority of persons with disabilities (an ex ante obligation), reasonable accommodation is required in those situations in which an environment, already accessible, must be adapted to the particular needs of a specific individual.68 Accordingly, the duty to provide reasonable accommodation is configured as an ex nunc obligation, which means that it is enforceable from the moment that an individual with an impairment needs it in a given situation.69 54. While the CRPD includes accessibility as a fundamental principle and as a vital precondition for the effective and equal enjoyment of civil, political, economic, social and cultural rights by persons with disabilities, 70 by means of universal design, reasonable accommodation seeks to achieve individual justice in the sense that non-discrimination or equality is assured, taking the dignity, autonomy and choices of the individual into account. Thus, a person with a rare impairment might ask for accommodation that falls outside the scope of any accessibility standard.71 Cf. Committee on the Rights of Persons with Disabilities, General Comment No. 2, Article 9: Accessibility, CRPD/C/GC/2, May 22, 2014, para. 3. 66 67 Convention on the Rights of Persons with Disabilities, Article 2. Cf. Committee on the Rights of Persons with Disabilities, General Comment No. 2, Article 9: Accessibility, CRPD/C/GC/2, May 22, 2014, paras. 25 and 26. 68 Cf. Committee on the Rights of Persons with Disabilities, General Comment No. 2, Article 9: Accessibility, CRPD/C/GC/2, May 22, 2014, para. 26. 69 Cf. Committee on the Rights of Persons with Disabilities, General Comment No. 2, Article 9: Accessibility, CRPD/C/GC/2, May 22, 2014, para. 4. 70 Cf. Committee on the Rights of Persons with Disabilities, General Comment No. 2, Article 9: Accessibility, CRPD/C/GC/2, May 22, 2014, para. 26. 71 20