European Union – Social security. Article 14(1)(a) of Council Regulation (EEC) No 1408/71, as amended and updated, and art 11(1)(a) of Council Regulation (EEC) No 574/72 should be interpreted as meaning that, when an institution of a member state to which workers had been posted made an application to the institution that had issued E 101 certificates for the review and withdrawal of those certificates in the light of evidence which supported the conclusion that those certificates had been fraudulently obtained or relied on, a national court could, in the context of proceedings brought against persons suspected of having used posted workers ostensibly covered by such certificates, disregard those certificates if it found evidence of such fraud. The Court of Justice of the European Union so held in a preliminary ruling in the course of proceedings regarding the posting of Bulgarian workers to Belgium.