Several European countries have laws that require that articles made of precious metals bear a hallmark guaranteeing the purity of the metal used before they can be sold. Dutch law required that articles of this type imported from other EU member states should bear a hallmark not only from the country of origin but also an additional Dutch mark. The question of whether this was lawful came before the European Court of Justice in the case of Ludomir Neeltje v. Barbara Houtwipper as a result of criminal proceedings brought against someone who sold such goods in the Netherlands which did not bear the additional Dutch hallmark. The German government intervened to observe that Dutch law in requiring additional hallmarking increased the cost of imported goods.

The Court decided that such an additional requirement was incompatible with the Treaty of Rome if the goods in question had been lawfully marketed and hallmarked in accordance with the laws of another EU member state providing guarantees of the independence of the hallmarking body as long as the information provided by the hallmark, in whatever form, is equivalent to that which is required by the legislation of the country into which the goods are being imported and the information given by the hallmark is intelligible to consumers in that country.