20Thus, in the context of applying the provisions of Regulation No 1049/2001, it has been held that the purpose of the obligation on the institution to state the reasons for its decision refusing to grant access to a document is, first, to provide the person concerned with sufficient information to make it possible to determine whether the decision is well founded or whether it is vitiated by an error which may permit its validity to be contested and, secondly, to enable the Courts of the European Union to review the lawfulness of the decision. The extent of that obligation depends on the nature of the measure at issue and the context in which it was adopted (see judgment of 25 April 2007, WWF European Policy Programme v Council, T‑264/04, EU:T:2007:114, paragraph 36 and the case-law cited).