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The non-written sources of European law: supplementary law

Supplementary law brings together the unwritten sources of European law having judicial origin. These sources are used by the Court of Justice as rules of law in cases where the primary and/or secondary legislation do not settle the issue. They include general principles of law and rules of public international law. Fundamental rights, which have long been seen by the Court of Justice as general principles of law, are gradually becoming elements of primary legislation.

In its case-law, the Court of Justice has taken a series of rules of law as a basis to bridge the gaps left by primary and/or secondary legislation. These are mainly public international law and general principles of law. These two categories overlap, the Court of Justice having developed general principles of law which was inspired by public international law.

Fundamental rights constitute a specific category of rules as they may form part of the primary law or supplementary law of the European Union (EU) depending on their source. Furthermore, since the 1970s, a shift has occurred as these fundamental rights are now tending to become a source of primary legislation rather than a supplementary law.

International law

International law is a source of inspiration for the Court of Justice when developing its case law. The Court cites written law, custom and usage.

The Court of Justice also considers that the EU must abide by the rules of international law. For example, the Court believes that the EU is a subject of law which can be held internationally liable vis-à-vis a non-member if it occasions any harm.

International law also constitutes a source of inspiration for the Court of Justice when drawing up its general principles of law. This is the case with the principles of, for example:

  • the obligation of good faith;
  • the pacta sunt servanda principle (pacts must be respected - agreements are legally binding on all parties concerned);
  • territoriality;
  • treaties lapse in the event of a fundamental change in circumstances.

However, the Court of Justice has also excluded certain principles of international law that it considers incompatible with the structure of the European Union, such as the principle of reciprocity in the fulfilment of state obligations.

General principles of law

General principles of law are unwritten sources of law developed by the case law of the Court of Justice. These principles have allowed it to implement rules in different domains of which the treaties make no mention, concerning the non-contractual liability of the EU, for example. The general principles of law may be:

  • common to national laws: the Court of Justice identified those principles common to all the national legal systems and which are compatible with EU objectives. For example, this is the case with legal certainty and legitimate expectation which protects an individual from unforeseeable amendments to the law;
  • derived from particular national laws: the Court of Justice took inspiration from the principles enshrined in certain national legal systems only. This is also the case when the Court must name the institution responsible for harm caused by the EU and it must determine the extent of the harm;
  • specific to the EU: the Court of Justice identified the principles specific to the EU even if the source of their inspiration was from a national legislation. This is the case with the solidarity between Member States, institutional balance and Community preference.

The specific case of fundamental rights:

There are three sources of fundamental rights in the EU:

Before the Treaty of Lisbon entered into force, the Charter of Fundamental Rights, the ECHR and the constitutional traditions of Member States formed part of EU law as general principles of law.

Subsequently, the Treaty of Lisbon enshrined the binding force of the Charter of Fundamental Rights in the founding Treaties. Furthermore, Article 6 of the Treaty on EU confers it with the same legal value as the Treaties. The Charter of Fundamental Rights has therefore become a source of primary law of the EU.

Moreover, Article 6 of the Treaty on EU keeps the ECHR and the constitutional traditions of the Member States as a source of the general principles of law. If necessary, the Court of Justice may refer to these principles in order to complement the fundamental rights protected in the Charter.

Finally, Article 6 of the Treaty on EU also provides the option for the EU to join the ECHR. An agreement relating to EU membership of the ECHR would need to be adopted unanimously by the Council and ratified by Member States. Moreover, a protocol regarding EU membership of the ECHR has been annexed to the Treaties. In particular, this protocol specifies that possible EU membership should not change its competences, nor affect the powers of its institutions.

Last updated: 20.08.2010
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