In the period 1859-1918, Romania built and consolidated a modern law system subject to fundamental principles that were found throughout Europe, with functional mechanisms and institutions. The adoption of the major codes - the Civil Code, the Code of Civil Procedure, the Criminal Code and the Code of Criminal Procedure - during the reign of Alexandru Ioan Cuza had a cardinal importance for the national legal system. The exercise of modern legislation initiated at that time, in a rhythm which was sometimes criticized, continued through the adoption of the 1866 Constitution or through the measures of the integration of Dobrogea in the Romanian law system. On the path opened by the generation of the Union of the Principalities, Carol I strengthened the beneficial force of law, building a state in which “only the law debated and approved by the nation, decides and governs”. The science of law and legal culture had in Romania, almost six decades after the Union of the Principalities, gathered through tradition and reform, an important dowry, a true “fulfilled state of law”. In the Old Kingdom there was, at the beginning of the 20th century, a fully achieved legal system that rightly expected to be the foundation of the legal system of Greater Romania.