The ECJ has, in Case C?48/09 P, ruled that the Lego brick cannot be registered as a trade mark because its shape is necessary to obtain a technical result. The most pertinent paragraphs of the decision read as follows.
45 First, the inclusion in Article 7(1) of Regulation No 40/94 of the prohibition on registration as a trade mark of any sign consisting of the shape of goods which is necessary to obtain a technical result ensures that undertakings may not use trade mark law in order to perpetuate, indefinitely, exclusive rights relating to technical solutions.
46 When the shape of a product merely incorporates the technical solution developed by the manufacturer of that product and patented by it, protection of that shape as a trade mark once the patent has expired would considerably and permanently reduce the opportunity for other undertakings to use that technical solution. In the system of intellectual property rights developed in the European Union, technical solutions are capable of protection only for a limited period, so that subsequently they may be freely used by all economic operators. […]