INTRODUCTION 
The Principle of Subsidiarity is fundamental to the functioning of the European Union (EU), and more specifically to European decision-making. In particular, the principle determines when the EU is competent to legislate, and contributes to decisions being taken as closely as possible to the citizen.
The principle of subsidiarity is established in Article 5 of the Treaty on European Union. It appears alongside two other principles that are also considered to be essential to European decision-making: the principles of conferral and of proportionality.
The Protocol on the application of the principles of subsidiarity and proportionality (See Protocol Nº 2 HERE) also defines the implementation of the principle of subsidiarity. In addition, the Treaty of Lisbon has considerably strengthened the principle of subsidiarity by introducing several control mechanisms in order to monitor its application.
DEFINITION
The principle of subsidiarity aims at determining the level of intervention that is most relevant in the areas of competences shared between the EU and the Member States. This may concern action at European, national or local levels. In all cases, the EU may only intervene if it is able to act more effectively than Member States. The Protocol on the application of the principles of subsidiarity and proportionality lays down three criteria aimed at establishing the desirability of intervention at European level:
- Does the action have transnational aspects that cannot be resolved by Member States?
- Would national action or an absence of action be contrary to the requirements of the Treaty?
- Does action at European level have clear advantages?
The principle of subsidiarity also aims at bringing the EU and its citizens closer by guaranteeing that action is taken at local level where it proves to be necessary. However, the principle of subsidiarity does not mean that action must always be taken at the level that is closest to the citizen.
Complementarity with the principles of conferral and of proportionality
Article 5 of the Treaty on European Union defines the division of competences between the Union and the Member States. It first refers to the principle of conferral according to which the Union has only those competences that are conferred upon it by the Treaties.
Subsidiarity and proportionality are corollary principles of the principle of conferral. They determine to what extent the EU can exercise the competences conferred upon it by the Treaties. By virtue of the principle of proportionality, the means implemented by the EU in order to meet the objectives set by the Treaties cannot go beyond what is necessary.
The Union can therefore only act in a policy area if:
the action forms part of the competences conferred upon the EU by the Treaties (principle of conferral);
in the context of competences shared with Member States, the European level is most relevant in order to meet the objectives set by the Treaties (principle of subsidiarity);
the content and form of the action does not exceed what is necessary to achieve the objectives set by the Treaties (principle of proportionality).
MONITORING THE PRINCIPLE OF SUBSIDIARITY
Mechanisms to monitor the principle of subsidiarity were put in place by the Protocol on the application of the principles of subsidiarity and proportionality. The Treaty of Lisbon reformed the above Protocol in order to improve and reinforce monitoring.
The Protocol, introduced by the Treaty of Amsterdam, provided for compliance with certain obligations during the actual drafting of legislation. Thus, before proposing legislative acts, the Commission must prepare a Green Paper. Green Papers consist of wide-ranging consultations. They enable the Commission to collect opinions from national and local institutions and from civil society on the desirability of a legislative proposal, in particular in respect of the principle of subsidiarity.
The Protocol also adds an obligation for the Commission to accompany draft legislative acts with a statement demonstrating compliance with the principles of subsidiarity and proportionality.
The Treaty of Lisbon innovates by associating national Parliaments closely with the monitoring of the principle of subsidiarity. National Parliaments now exercise twofold monitoring:
- they have a right to object when legislation is drafted. They can thus dismiss a legislative proposal before the Commission if they consider that the principle of subsidiarity has not been observed (see file “National Parliaments”);
- through their Member State, they may contest a legislative act before the Court of Justice of the EU if they consider that the principle of subsidiarity has not been observed.
The Treaty of Lisbon also associates the Committee of the Regions with the monitoring of the principle of subsidiarity. In the same way as national Parliaments, the Committee may also contest, before the Court of Justice of the EU, a legislative act that does not comply with the principle of subsidiarity.