That solution, which has been established in case-law in relation to the admissibility of an appeal, must be extended to the question of the admissibility of a plea. The principle underlying the rules governing the admissibility of an appeal and, in particular, those relating to the time-limits for lodging appeals, namely the principle of legal certainty, also justifies the application of an analogous solution as regards the admissibility of a plea.

The time-limits laid down in Articles 90 and 91 of the Staff Regulations for lodging complaints and appeals are intended to ensure legal certainty. They are therefore mandatory and cannot be left to the discretion of the parties or the Court. The fact that the defendant institution does not formally raise, at the stage of proceedings before the Court, an objection of inadmissibility on the ground that the appeal is time-barred does not dispense the Court from verifying whether those time-limits have been complied with.

An act adversely affecting an official may not be challenged even in part after the expiry of the period for lodging an appeal. If such an act has not been contested within the time-limits laid down for that purpose, the person concerned cannot be allowed to circumvent those time-limits by putting forward, in other court proceedings, a plea which could lead to essentially the same result as an action for annulment brought against the act adversely affecting him.

The time-limits for lodging appeals are mandatory and derogations may be made only exceptionally, by reason of the occurrence of a substantial new fact. In order not to infringe the principle of legal certainty, even the subsequent discovery by an appellant of a preexisting plea or factor cannot, in principle, be regarded as a new fact capable of justifying the granting of leave to appeal out of time.

The exercise of the discretion enjoyed by the institutions with respect to the holding of competitions, in particular as regards the determination of the conditions of admission, must be compatible with the mandatory provisions of the first paragraph of Article 27 and Article 29(1) of the Staff Regulations. The terms in which the first paragraph of Article 27 of the Staff Regulations defines the aim to be pursued by any recruitment and in which Article 29(1) of the Staff Regulations lays down the framework for the procedures for filling vacant posts are mandatory. That discretion must therefore always be exercised in the light of the requirements of the posts to be filled and, more generally, the interests of the service.

In that regard, in the context of internal competitions, the condition of admission that candidates must be members of the staff covered by the Staff Regulations is justified in relation to Article 29 of the Staff Regulations and to the scheme of those regulations, as well as in relation to the interests of the service.

The holding of an internal competition, as provided for by that article, is mentioned as one of the possible avenues of recruitment, together with promotion or internal transfer, as provided for by Article 29(1)(a) of the Staff Regulations, and transfer from another institution, as provided for by Article 29(1)(c) of the Staff Regulations. Promotion, internal transfer and inter-institutional transfer are all measures applicable to staff who are subject to the Staff Regulations. Consequently, the decisive criterion for interpreting the concept of staff within the institution, which determines participation in an internal competition, is not the particular situation of the candidates, but the relationship between the persons concerned and the institution. In order for the condition of admission to a competition, which requires candidates to be members of the staff within the institution, to be fulfilled, that relationship must be one governed by public law. It cannot be regarded as consistent with the scheme of the Staff Regulations for the term ‘internal’ used in the Staff Regulations to refer to persons other than those holding positions under the Staff Regulations.

(see paras 52, 56, 61)

See: Opinion of Advocate General Gand in Case 16/64 Rauch v Commission [1965] ECR 135; T-40/96 and T-55/96 de Kerros and Kolin-Bergé v Commission [1997] ECRSC I-A-47 and II-135, para. 40; T-294/97 Carrasco Benitez v Commission [1998] ECRSCI-A-601 and II-1819, para. 48; T-214/99 Carrasco Benitez v Commission [2000] ECRSC I-A-257 and II-1169, para. 53