On 6 April 2023, Mees Vergouwen, tax adviser, obtained his PhD from Leiden University on 'The effect of directives in the area of direct taxation on the interpretation and application of tax treaties'.

The research focuses on determining the effect that directives, as instruments from the Council of the EU, may have on the interpretation and application of tax treaties under the laws of public international law and the laws of the EU. In this respect, it is concluded that the effect of the directives does not extend so far so to affect tax treaties in such a way that tax treaties cannot stand in the way of a Member State achieving the result of a directive. Therefore, it is recommended that EU Member States conclude a multilateral treaty that provides that tax treaties between EU Member States are only applicable to the extent compatible with provisions of directives, while also clarifying – in directives – what the intended effect of a directive is with respect to tax treaties concluded by Member States with third states.

Mees is part of the tax practice group at De Brauw and focuses on advising clients and tax litigation. He is also the author of numerous publications on (international) tax law and teaches international and European tax law at Leiden University.