This study deals with the impact of the free movement rules in the EC Treaty on tax treaties in the internal market. This is a highly relevant issue since a provision in breach of the free movement rules is inapplicable. The potential far-reaching consequences following the preclusion of tax treaty provisions makes it important for taxpayers and governments of the Member States of the EU to predict when a provision in a tax treaty may be in conflict with free movement law.

This thesis identifies the rights and obligations stemming from the free movement rules. As they are not very detailed, the case law is crucial. Hence, this thesis includes extensive case law studies, focusing primarily on cases where the Court of Justice of the European Communities (ECJ) has interpreted the free movement rules in relation to tax treaty provisions and unilateral income tax legislation. This study provides a systematization of such case law, highlighting consistencies and inconsistencies.

Furthermore, whether the free movement provisions prescribe a most-favoured-nation treatment is examined. This is relevant to this study as an answer in the affirmative would have a considerable impact on tax treaties concluded between EU Member States.