The European Court of Justice ('ECJ') answered preliminary questions from the Dutch Supreme Court (Hoge Raad) on 14 December 2016. The central issue in this case was whether there is room for a proportionality test if a tenderer is guilty of grave professional misconduct and the tender documents state that such behaviour must result in exclusion. The misconduct in this case resulted from an earlier infringement of competition rules by one of the tenderers, for which it was fined. In its answers, the ECJ held that Member States are allowed to require a contracting authority to assess, in accordance with the principle of proportionality, whether it is in fact appropriate to exclude from a public contract a tenderer which has been guilty of grave professional misconduct. However, at the time of this tender procedure, the proportionality test did not follow from the tender documents or the Dutch procurement rules, but only from the Explanatory Memorandum (Nota van Toelichting). In those circumstances, the tender documents prevail and a proportionality test is therefore not allowed, according to the ECJ. Under the current Dutch (and European) procurement rules, the outcome would be different because a proportionality test is now included in the law itself. However, this test only covers the exclusion grounds that are explicitly stated in the Dutch Procurement Act (such as grave professional misconduct). This means that in case of other reasons for exclusion (e.g. missing documents in the tender), a proportionality test is only allowed if that is explicitly provided for in the tender documents.