Advocate General Mazák (the AG) has given his Opinion on whether a body providing insurance against accidents at work and occupational diseases is an "undertaking" for the purposes of EC competition law. Case C-350/07 came before the European Court of Justice (ECJ) on a preliminary reference from a court in Saxony (Germany). The background to the case is that the insurance body concerned, MMB provided statutory occupational accident insurance company to a private company, Kattner. In November 2004, Kattner decided to cancel its affiliation with MMB on the basis that it had decided to obtain private insurance. MMB advised Kattner it could not opt out of the affiliation. Kattner appealed the decision claiming that compulsory affiliation breaches EC competition law. One issue referred to the ECJ was whether MMB is an "undertaking" under Articles 81 & 82 EC. In his Opinion the AG's took the view that a body operating a social security scheme based on the principle of solidarity would not be an "undertaking" where certain elements of the scheme are subject to State supervision. The AG also took the view that the compulsory affiliation of certain employers to insurance associations operating such social security schemes did not breach the EC Treaty rules on free movement of services.