The freedom of movement for workers is a policy chapter of the acquis communautaire of the European Union. It is part of the free movement of persons and one of the four economic freedoms: free movement of goods, services, labour and capital. Article 45 TFEU (ex 39 and 48) states that:
The right to free movement has both 'horizontal' and 'vertical' direct effect, such that a private citizen can invoke the right, without more, in an ordinary court, against other persons, both governmental and non-governmental.
The Treaty of Paris (1951) establishing the European Coal and Steel Community established a right to free movement for workers in these industries and the Treaty of Rome (1957) provided a right for the free movement of workers within the European Economic Community. The Directive 2004/38/EC on the right to move and reside freely assembles the different aspects of the right of movement in one document, replacing inter alia the directive 1968/360/EEC. It also clarifies procedural issues, and it strengthens the rights of family members of European citizens using the freedom of movement. According to the official site of the European Parliament, the explanation of the freedom of workers goes as follows:
Freedom of movement and residence for persons in the EU is the cornerstone of Union citizenship, which was established by the Treaty of Maastricht in 1992. Its practical implementation in EU law, however, has not been straightforward. It first involved the gradual phasing out, of internal borders under the Schengen agreements, initially in just a handful of Member States. Today, the provisions governing the free movement of persons are laid down in Directive 2004/38/EC on the right of EU citizens and their family members to move and reside freely within the territory of the Member States. However, the implementation of this directive continues to face many obstacles.