<P> The Court can sit in plenary session, as a Grand Chamber of fifteen judges (including the president and vice-president), or in chambers of three or five judges . Plenary sittings are now very rare, and the court mostly sits in chambers of three or five judges . Each chamber elects its own president who is elected for a term of three years in the case of the five - judge chambers or one year in the case of three - judge chambers . </P> <P> The Court is required to sit in full court in exceptional cases provided for in the treaties . The court may also decide to sit in full, if the issues raised are considered to be of exceptional importance . 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 . </P> <P> The court acts as a collegial body: decisions are those of the court rather than of individual judges; no minority opinions are given and indeed the existence of a majority decision rather than unanimity is never suggested . </P> <P> The idea behind European Union legislation is that each Member State shall incorporate into its own domestic law the principles laid down in the Union legislation . 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 and of the provisions laid down by the competent Community institutions To enable it to carry out that task, the Court has broad jurisdiction to hear various types of action . The Court has competence, among other things, to rule on applications for annulment or actions for failure to act brought by a Member State or an institution, actions against Member States for failure to fulfil obligations, references for a preliminary ruling and appeals against decisions of the General Court . </P>

History of the court of justice of the european union