Article 45(2) of Directive 2004/18 does not provide for uniform application at EU level of the grounds of exclusion it mentions, since the Member States may choose not to apply those grounds of exclusion at all or to incorporate them into national law with varying degrees of rigour according to legal, economic or social considerations prevailing at national level. In that context, the Member States have the power to make the criteria laid down in Article 45(2) less onerous or more flexible. In that connection, as regards national legislation which requires a contracting authority which establishes that the tenderer has been guilty of grave professional misconduct, to determine, in accordance with the principle of proportionality, whether the tenderer should in fact be excluded, that assessment of the proportionality makes the application of the ground of exclusion relating to grave professional misconduct laid down in Article 45(2)(d) of Directive 2004/18 more flexible. Furthermore, it follows from recital 2 thereof that the principle of proportionality applies in a general manner to public procurement procedures.

The provisions of Directive 2004/18 on the coordination of procedures for the award of public works contracts, public supply contracts and public service contracts, in particular those of Article 2, of and Annex VII A, point 17, thereto, read in the light of the principle of equal treatment and the obligation of transparency which derives from that, must be interpreted as precluding a contracting authority from deciding to award a public contract to a tenderer which has been guilty of grave professional misconduct on the ground that the exclusion of that tenderer from the award procedure would be contrary to the principle of proportionality, even though, according to the tender conditions of that contract, a tenderer which has been guilty of grave professional misconduct must necessarily be excluded, without consideration of the proportionality of that sanction.

Some of the economic operators concerned, although aware of the exclusion clause in the contract documents and knowing that they have been guilty of professional misconduct likely to be considered to be grave, may be tempted to submit a tender in the hope of being exempt from the exclusion on the basis of a subsequent assessment of their situation in the application of the principle of proportionality, pursuant to the national legislation at issue in the main proceedings, while others, in a comparable situation, will not submit such a tender based on the terms of the exclusion clause which does not mention such an examination of proportionality. The latter situation, in particular, is likely to concern the economic operators from other Member States who are less familiar with the terms and detailed rules of application of the relevant national legislation. That is particularly true in a situation in which the contracting authority’s obligation to carry out such an assessment of proportionality of an exclusion for grave professional misconduct does not derive from the terms of the applicable national measure, but only from the explanatory memorandum relating to it. Therefore, the assessment of the exclusion at issue in the light of the principle of proportionality, where the tender conditions of the contract concerned provide for the rejection of tenders which are covered by such an exclusion clause without any assessment of that principle, is liable to place the economic operators concerned in an uncertain position and adversely affect the principle of equal treatment and compliance with the obligation of transparency.

(see paras 41-44, operative part 2)