On 5 April 1990, the European Parliament’s Institutional Committee publishes a working document on the principle of subsidiarity. This document explores the implementation of this principle in the European integration process, including the internal and external competences of the European Community and the balance of powers between the European Community and the Member States. It also addresses the insertion of the concept of subsidiarity in the EC Treaties, the European Parliament’s position on this concept and the mechanisms introduced to ensure the implementation of subsidiarity.