The Legitimation of Soft Law in the Context of the Reservation of Law: Limits and Challenges in Tax Law

This study examines the increasing influence of soft law norms in the Portuguese legal system. Due to its flexibility and lack of binding force, soft law has become an alternative tool for consensual regulation, particularly in contexts of legal pluralism. However, its incorporation into domestic law, guided by national sovereignty, may contribute to the fragmentation of the transnational legal order and undermine the coherence of the European legal space. Moreover, although its reception occurs through parliamentary deliberation, there are concerns that this practice serves as a channel for introducing norms from supranational bodies that are often removed from institutional normative control. This research aims to investigate the legitimacy and limits of this practice, with special emphasis on tax law, where the principle of legal reservation demands strict rigor in the creation of tax norms.

Keywords: soft law; tax law; reservation of law; globalization; legal pluralism