Where the contested act is merely confirmatory, an action is admissible only if the act confirmed is challenged within the prescribed time-limits.

However, the existence of substantial new facts may justify the submission of a request for reconsideration of a previous decision which has become definitive. If a measure constitutes the reply to a request in which substantial new facts are relied on, and whereby the administration is requested to reconsider its previous decision, that measure cannot be regarded as merely confirmatory in nature, since it constitutes a decision taken on the basis of the supposed substantial new facts and thus contains a new factor as compared with the previous decision. Thus, after reconsideration, based on substantial new facts, of a decision which has become definitive, the institution concerned must take a new decision, the legality of which may where necessary be challenged before the EU judicature. However, in the absence of substantial new facts, the institution is not required to reconsider its earlier decision.

It follows that a measure is regarded as adopted after a re-examination of the circumstances, which prevents it from being confirmatory in nature, where that measure was adopted either at the request of the person concerned, or at the initiative of its author, on the basis of substantial factors which were not taken into account at the time of adoption of the preceding measure. However, if the matters of fact or law on which the new measure is based are not different from those which justified the adoption of the preceding measure, that new measure is purely confirmatory of the preceding measure.

In the context of an annulment action brought against a Commission decision refusing to amend an earlier decision and based on an application by analogy of the legal reasoning followed by the EU judicature in judgments delivered after the adoption of the said earlier decision, the fact that those judgments are subsequent to the said decision does not make them new factors.

A judgment on a request for a preliminary ruling does not have constitutive, but purely declaratory effect, so that its effects arise, in principle, at the date of entry into force of the rule interpreted. Such a judgment thus merely clarifies the existing state of the law, as it could have and should have been understood by the administration at the time of adoption of the decision.

In the case of judgments annulling similar decisions, the only purpose of considering the grounds of the judgment which set out the precise reasons for the illegality found by the EU judicature is to determine the exact meaning of the ruling made in the operative part of the judgment. Therefore, the authority of a ground of a judgment annulling a measure cannot apply to the situation of persons who were not parties to the proceedings and with regard to whom the judgment cannot therefore have decided anything whatsoever. In those circumstances, although Article 263 TFEU requires the institution concerned to ensure that any act intended to replace the annulled act is not vitiated by the same irregularities as those identified in the judgment annulling the original act, that provision does not mean that it must, at the request of interested parties, re-examine identical or similar decisions allegedly affected by the same irregularity, addressed to addressees other than the applicant.

Such judgments cannot be regarded as being new factors. The mere fact that neither the administrative body, at the time of adoption of a decision, nor the addressee thereof, before the expiry of the time limit for bringing an action against that decision, considered or relied on legal interpretation or legal reasoning endorsed by the EU judicature in a subsequent judgment cannot affect the definitive nature of the decision concerned.

It is true that there are limits on the principle of legal certainty in relation to administrative decisions contrary to EU law that have become definitive, which may warrant their being modified in certain circumstances. However, those limits are not applicable when the party requesting reconsideration of the decision that has become definitive has not exhausted the remedies open to it to challenge that decision.

(see paras 58-60, 66-73)