the contested  decision is not [merely] vitiated either by a 'procedural irregularity' or a 'formal defect', since the failure to state reasons does not constitute such a defect, but it rather lacks an "essential element", which effectively determines its nullity. In this case, therefore, there is a subjective claim preclusion between the parties [res iudicata] and, accordingly, the Commission, being under the obligation to give effect to the judgments of the Court in Italy and Wam v Commission [T-304/04 and T-316/04] and Commission v Italy and Wam [C-494/06], could not "in any way have adopted a new decision on the matter". The Court should therefore "for this [reason] only", have annulled the contested decision (C-560/12 P, para 6, own translation from Italian).
However, in Wam the CJEU does not show the same appetite for the development of a strong limit on the Commission's ability to reopen a case after losing it on appeal (a sort of procedural estoppel or ne bis in idem), and dismisses the argument on the (very formal basis) that
15 By the first part of the first plea, it should be noted that the applicant merely submits that, for the mere fact [of the existence of] the judgments of the Court in Italy and Wam v Commission and Commission v Italy and Wam, the Commission would have been in any case precluded from adopting a new decision.
16 In that regard it should be noted that the argument concerning that matte is limited to a dozen lines on pages 26 and 27 of the appeal, the substance of which is taken up in paragraph 7 [sic, 6] of this judgment.
17 However, such an argument, marred by a lack of precision, clearly does not fulfill the conditions laid down in Article 169, paragraph 2, of the Rules of Procedure of the Court. Consequently, it must be rejected as inadmissible (C-560/12 P, paras 15-17, own translation from Italian).
7 [ ...] the Court erred in holding that the Commission did not have an obligation to open a new contradictory investigation procedure with the national authorities. Contrary to what the Court found, the point would not have been to establish, in general and in theory if, after a judgment of annulment for failure to state reasons, the Commission could or could not take up the procedure from the adoption of the [annulled] act.
8 The Italian Republic considers that, given that the Commission has "renew[ed] completely" the examination of all matters in the contested decision, introducing new facts, it has hence recognized that the "defects criticized", despite being considered as defects of the duty to state reasons, actually had substantial implications that made it necessary to "redo from scratch" the 2004 decision.
9 The Italian Republic considers that the [...] factual elements consisting of the alleged "relative strengthening" of Wam and the alleged "freeing up of resources" could never have been deducted from the [initial] investigation procedure. Consequently, them being decisive elements for the demonstration of the existence of aid, the Commission should have opened a new adversarial procedure with the parties concerned [...]
10 The Commission claims that the first part of the first plea is unfounded. It points out that the annulment of the 2004 decision was based on a lack of motivation because [...] that decision did not explain in what way the aid in question could affect competition and trade between Member States. On the contrary, the Court failed to criticize the inquiry into the matter as carried out during the administrative procedure, nor did it identify any deficiency in this regard (C-587/12 P, paras 7-10, own translation from Italian).
11 It should be remembered that in the judgment of the Court in Italy and Wam v Commission as well as in the judgment in Commission v Italy and Wam, the investigation conducted by the Commission on the aid in question was not at all criticized.
12 [...] the General Court correctly pointed out that, according to settled case-law, the procedure for replacing an unlawful act that has been cancelled can be resumed at the point at which the illegality occurred, that the cancellation of a Union act does not necessarily affect the preparatory acts and, furthermore, that the annulment of an act that puts an end to an administrative proceeding which comprises several stages does not necessarily entail the annulment of the entire procedure prior to the adoption of the contested measure for whatever reason, procedural or substantive, taken into account in the judgment of annulment.
13 [...] the Court also correctly pointed out that if, despite of the investigations that enable a comprehensive analysis of the compatibility of the aid, the Commission's analysis is found to be incomplete, and it involves the illegality of the decision, the procedure for replacing such a decision may be resumed at that point making a new analysis of the investigatory measures.
14 As regards the present case [...] the Court stated that the illegality of the 2004 decision [...] concerned the inadequate statement of reasons thereof. [...] the Court has, in fact, merely stated that this decision did not contain sufficient arguments that would allow the conclusion that they met all the conditions for the application of Article 107, paragraph 1, TFEU which was confirmed by the Court in its judgment in Commission v Italy and Wam. The illegality of the 2004 decision did not affect the proceedings before it. No argument leads to the conclusion that that procedure was, in itself, vitiated by any illegality.
15 As to the argument put forward by the applicant's claim that the Court failed to take account of the fact that the Commission has completely revisited the examination of all the evidence in the file and introduced new elements, it should be noted that this argument is not supported by anything which could demonstrate a misrepresentation of the facts relating to it by the Court.
16 As regards the applicant's claim that the Court, in the remainder of its reasoning, ignored any arguments to refute the conclusion set out in paragraph 50 of the judgment under appeal, the Court notes that, in paragraph 57 of that judgment, the Court stated that the circumstances relating to the strengthening of Wam's position and the release of resources were correctly assessed in the contested decision. The Court added in such a point that, in any case, it was not new factual circumstances, but considerations arising from the analysis of the Commission, based on elements with respect to which nothing allowed it to believe that they were not known at the time when the decision was taken in 2004. [...]
19 In these conditions [...] the General Court correctly concluded that the execution of the judgment of the Court in Italy and Wam v Commission and the judgment in Commission v Italy and Wam did not require the Commission to take on again the whole process provided for in Article 108 TFEU and that the Commission had erred, as a result of the same judgment, by not initiating a new formal investigation procedure.
20 The first part of the first plea is therefore unfounded (C-587/12 P, paras 11-20, own translation from Italian, emphasis added).