162The purpose of the obligation to state the reasons for an act adversely affecting a person, as provided for in Article 253 EC, is, first, to provide the person concerned with sufficient information to make it possible to determine whether the act is well founded or whether it is vitiated by an error which may permit its validity to be contested before the EU judicature and, second, to enable the latter to review the lawfulness of the decision. The obligation to state reasons therefore constitutes an essential principle of Community law which may be derogated from only for compelling reasons. The statement of reasons must therefore in principle be notified to the person concerned at the same time as the act adversely affecting him, since a failure to state the reasons cannot be remedied by the fact that the person concerned learns the reasons for the act during the proceedings before the EU judicature (see, to that effect, Case T-228/02Organisation des Modjahedines du peuple d’Iran v Council [2006] ECR II-4665, paragraphs 138 to 140, and the case-law cited).