The general aim of subsidiarity is to guarantee a degree of independence to a lower authority from a higher authority. It is concerned with how power is shared between them. In EU terms, the principle means that the EU can only make legislation if this is more effective than Member States making their own legislation. The principle sets out to ensure that decisions are made at the lowest possible level The principle is intended to achieve this but it is not guaranteed.
Subsidiarity is about how the EU exercises its competences. So where the EU does not have exclusive competence, for example, in criminal matters, the principle aims to protect the ability of Member States to take decisions and take actions. However, the principle should also permit intervention by the Union when the objectives of an action cannot be satisfactorily achieved by Member States ‘by reason of the scale and effects of the proposed action’.
Since the coming into force of the Lisbon Treaty, the EU legislation that is proposed by Council of Ministers, the European Parliament and the European Commission is carefully scrutinized by national parliaments to ensure that it complies with the principle of subsidiarity.
The principle was formally recognized in EU law by the Treaty of Maastricht. A statement on the principle is now found at Article 5 TEU.