In order to determine which translation concept is needed by translators in Spain, we will examine how the concept of translation is envisaged by Spanish law in keeping with today’s international sociological context. Only after examining the law can the legal translation concept be determined. Then, applying functionalism to the legal context, we will analyze whether the main function of the document, that is, its legal effectiveness, is preserved. The fundamental criterion required is the legal effectiveness of the legal document to be translated. Such effectiveness is defined in the context of an international collaboration in which foreign law or documents need to be recognized or implemented in a country according to the principles of international law. Such international collaboration is based on the acknowledgement of the common ground of the countries involved (jurilinguistic universals) and on respect for the differences.