Asda has lost its battle to sell cheaper Parma ham sliced and packaged in the UK.
European judges ruled the meat can only be sold as Parma ham if it is sliced and packed in Parma itself.
Asda had been slicing and packaging the meat at a plant in Wiltshire and said the move allowed it to keep the prices low.
The legal battle began in 1997 when the Parma ham consortium, Consorzio del Prosciutto di Parma, claimed the law in Italy stated that the product had to be packed and sliced in the region.
Asda's view that Italian law could not be applied under UK law was backed by the European Court's advocate general, but the full court overturned the decision.
The court stated that under the EU's Protected Designation of Origin law, Parma must be sliced and packed in the region.
An Asda spokesman said: "The court has been duped by the Parma producers' attempt to push up the price of their products."
The retailer, however, is still able to slice the ham and sell it as Parma on its deli counters.
Stefano Fanti, MD of the consortium, said: "This is an important day for the 200 producers of Parma ham. Control over the whole process guarantees quality and authenticity."