​The purposes of the operation of the Preliminary Ruling procedure are to provide consistency throughout the European Union on the interpretation of the provision of the European Union law treaties and to provide definitive interpretation 

​The procedures of the preliminary ruling begins with the national courts or tribunals based on their own discretion request for a ruling. 

It is an obligation for the national courts of the last resorts to refer the case and request for the ruling with the few exceptions

The first exception is based on the fact that the point of law has been decided based on the previous case by the European Court of Justice as in the case of de Costa or due to its irrelevancy or the answers are obvious / acted Clair as in CILFIT

The ruling from the European Court of Justice should be applied in all cases by the national courts of the member states.

​Urgent procedure is considered in sensitive issues touching the concern in the area of freedom, security and justice for example in the case of Inga Rinau ( Child Custody ) 

​The functional test begins with deciding whether the body is a court or tribunal 

The main focus is not on the name which is immaterial but focusing on the judicial function that the Body is performing. Cases such as Victoria film and Norsdee indicates the rejection of the preliminary ruling procedure due to the inability to establish the valid existence of the body as the court or tribunal 

The criteria need to be considered in establishing courts or tribunal include: 
-whether the Body is established by law 
-whether the body is permanent 
-whether the body is independent (Schmidt) 
-whether the body has compulsory jurisdiction 
-whether the body applies rule of law and inter partes procedure ( Dorsch ) 

​Problems with preliminary ruling procedure are ( mostly associated with delay in the reaching the ruling) are :
-the prolongation of the dispute in the national courts
-this may lead to the lack of encouragement to pursue the rulings by the national courts or tribunals The national courts or tribunals may interpret the European Union legislation themselves. This will result in the fragmentation of the views and meaning of the European Union law. 

The solutions for the above mentioned problems may include the part where The Nice Treaty conferred jurisdiction to the General courts on specific issues which are still subjects to review and referral by the European Court of Justice. 

The concepts of courts and tribunals are redefined

The restriction of the access to the European Court of Justice by the national courts.

The abolishment of the mandatory referral to the national Supreme Court

Any reform procedures will be carefully evaluated to guarantee the consistency with the European Union legislation 

Decentralisation with the formation of new European Union Courts. Restyled of the European High Court of Justice which hears any appeal.

​The impact of the the preliminary ruling procedure are the development of several key principles of the European Union Law by the European Court of Justice. These principles may include state liability, direct effect and supremacy. The new cases give opportunities for the European Court Court of Justice to develop new European Union law.