The Judges and Advocates-General are appointed by common accord of the governments of the member states[7] and hold office for a renewable term of six years.

They can question the parties involved and then give their opinion on a legal solution to the case before the judges deliberate and deliver their judgment.

The intention behind having Advocates General attached is to provide independent and impartial opinions concerning the Court's cases.

[14] As of 2003, Advocates General are only required to give an opinion if the Court considers the case raises a new point of law.

They are responsible for the Registry as well as for the receipt, transmission and custody of documents and pleadings that have been entered in a register initialled by the President.

[2] Sitting as a Grand Chamber is more common and can happen when a Member State or a Union institution, that is a party to certain proceedings, so requests, or in particularly complex or important cases.

[19] It is the responsibility of the Court of Justice to ensure that the law is observed in the interpretation and application of the Treaties of the European Union.

The court has decided that if the European Commission does not send the formal letter to the violating member state no-one can force them.

[21] If that procedure does not result in termination of the failure by the Member State, an action for breach of Union law may be brought before the Court of Justice.

[22] By an action for annulment under Article 263 (ex Article 230) of the Treaty on the Functioning of the European Union, the applicant seeks the annulment of a measure (regulation, directive, decision or any measure with legal effects) adopted by an institution, body, office or agency of the EU.

Under Article 268 of the Treaty on the Functioning of the European Union (and with reference to Article 340), the Court of Justice hears claims for compensation based on non-contractual liability, and rules on the liability of the Union for damage to citizens and to undertakings caused by its institutions or servants in the performance of their duties.

Whilst the Court of Justice is, by its very nature, the supreme guardian of Union legality, it is not the only judicial body empowered to apply EU law.

To ensure the effective and uniform application of Union legislation and to prevent divergent interpretations, national courts may, and sometimes must, turn to the Court of Justice and ask that it clarify a point concerning the interpretation of Union law, in order, for example, to ascertain whether their national legislation complies with that law.

In this way, a number of important principles of Union law have been laid down in preliminary rulings, sometimes in answer to questions referred by national courts of first instance.

Rulings end with a dictum which summarises the decision which the Court has made and may direct how costs are to be managed.

On 7 February 2014, the German Constitutional Court referred its first case to the ECJ for a ruling on a European Central Bank program.

Luxembourg City was chosen as the provisional seat of the Court on 23 July 1952 with the establishment of the European Coal and Steel Community.

Future judicial bodies (Court of First Instance and Civil Service Tribunal) would also be based in the city.

With the Treaty of Nice Luxembourg attached a declaration stating it did not claim the seat of the Boards of Appeal of the Office for Harmonisation in the Internal Market – even if it were to become a judicial body.

[34] Over time ECJ developed two essential rules on which the legal order rests: direct effect and primacy.

The court first ruled on the direct effect of primary legislation in a case that, though technical and tedious, raised a fundamental principle of Union law.

[35] The court ruled that the Community constitutes a new legal order, the subjects of which consist of not only the Member States but also their nationals.

Consequently Community law may, if appropriately framed, confer rights on individuals which national courts are bound to protect.

[38] In that decision the Court comprehensively ruled out any use by the Member States of the retaliatory measures commonly permitted by general international law within the European Economic Community.

[39] Commission v Luxembourg and Belgium also has a logical connection with the nearly contemporaneous Van Gend en Loos and Costa v ENEL decisions, as arguably it is the doctrines of direct effect and supremacy that allow the European legal system to forgo any use of retaliatory enforcement mechanisms by the Member States.

[40] Links between the direct effect doctrine and the suppression of inter-state retaliation between the EU member states can be found in many of the landmark early decisions of the European Court of Justice, and in the writings of the influential French judge, Robert Lecourt, perhaps the most important member of the Court between 1962 and 1976.

He was particularly critical of the court's judgment Mangold v Helm, which over-ruled a German law that would discriminate in favour of older workers.