34However, the particularly sensitive and essential nature of the interests protected by Article 4(1)(a) of Regulation No 1049/2001, combined with the fact that access must be refused by the institution, under that provision, if disclosure of a document to the public would undermine those interests, confers on the decision which must thus be adopted by the institution a complex and delicate nature which calls for the exercise of particular care (judgment of 1 February 2007, Sison v Council, C‑266/05 P, EU:C:2007:75, paragraph 35).