Between the nineteenth and twentieth centuries, with the multiplication of the State’s tasks, the financial needs relating to the organization of new public services led scholarship to question the traditional theory that considered tax law as a law of exception, launching a review of the basic principles that regulate the interpretation of financial law. In the 1930s, with the establishment, together with the central State administration, of a system of authorities involved in economic management and public finance, a financial system for special purposes appeared, which also called for a review of the traditional institutions of tax law. To meet such needs, Griziotti and Vanoni claimed that tax rules could be interpreted by analogy. However, at that time, in Europe there were also attempts to place the interpretation of tax legislation beyond the rule of law. In 1941, Giannini took part in the debate with an essay on the interpretation of tax laws («L’interpretazione e l’integrazione delle leggi tributarie»), with the aim to answer, in terms of legal theory, the increasing needs of public financial management while maintaining the rule of law and the principles of legal positivism.