This chapter examines the principle of the legality of taxation in the context of the rule of law. It begins with an exploration of the legality of taxation in international and EU Law, providing a comparative overview and delving into the specific case of Sweden. The authors discuss how this principle is not explicitly stated as a fundamental right in the European Charter of Human Rights and Fundamental Freedoms but can be derived from its provisions. The Court of Justice of the European Union recognizes it as a general principle, necessitating that tax obligations and their substantive elements be defined by law.

The article then focuses on the Swedish interpretation of the principle, tracing its evolution and current application. It highlights the nuances in the Swedish legal system, where the principle of legality in tax law is interpreted as a general rule that taxation must be lawful and in accordance with the principles of the rule of law. This includes a discussion of the role of the Swedish Parliament in enacting tax laws and the interpretative approaches of the Supreme Administrative Court.

In conclusion, the paper emphasizes the principle of legality as an integral part of a larger legal system grounded in the rule of law. It addresses the challenges and complexities in applying this principle, especially when harmonizing national and EU law principles in tax cases.