The preliminary reference procedure under Article 267 of the TFEU (Treaty of Functioning of the EU  means that if EU law is to be supreme it must have equal effect in all member states. In order to do this, the meaning and effect must be determined by the CJEU (Court Justice of the European Union). To avoid issues arising the Treaty provides this procedure so the National Courts can consult if necessary to the CJEU on issues covered only under Article 267 of Union Law. The principle of Article 267 procedure is to cooperate between the CJEU and the courts of MSâ€™s. The CJEU has an important role to play, and interpret matters of EU law. They can be asked questions only on: interpretation of the treaties and validity of Acts of intuitions. The jurisdiction of the CJEU doesnâ€™t extend any further than to questions put by the National Courts. The Treaty Article 267 works to set an alliance with the National Courts and the CJEU, this is so a boundary is set which the CJEU powers and the National Courts apply. The use of Article 267 is intended to be of a harmonious nature, so that it is clear the CJEU interprets and the national courts apply. The objective of Article 267 is to create independence for National Courts, also at the same time prevent â€œa body of case law not in accord with the rules of Community Law from coming into existence in any Member Stateâ€ [Case 107/76 Hoffmann La Roche v Centrfarm]. The purpose of the preliminary reference is to ensure correct interpretation of Community law in all MSâ€™s. Article 267 is essential for preserving Community character of the law established by the Treaty and has the obligation to see through that the law is the same in all MSâ€™s of the Community. It should be clear that the preliminary reference does not have the same function as an appeal. The National courts take the decision to refer the case, and can refer questions to the CJEU to exercise their discretion on a certain matter of a case. The CJEU and the National court have set guidelines on when to refer a matter and the discretion that should be exercised. This is called the â€˜Guidance on Referrals by National Courts for Preliminary Rulingsâ€™ . The National Court will then decide whether it is necessary to send a reference. If the CJEU has already implied the answer needed from another case or it is irrelevant , or there is no scope of doubt as it is obvious and the same view would be shared in all courts of the MSâ€™s, which is known as the French principle of â€œacte clairâ€. Then there will be no need to send a reference to the CJEU. An example of the preliminary reference procedure would be a conflict with a national law in a MS and union law. The National courts should submit questions to the CJEU to clarify how to apply the law correctly. The preliminary reference procedure is shown through the case of Costa V ENEL  as the effectiveness of the PRP works essentially well but occasionally between the CJEU and National Courts there has been friction. Due to the National Courts submitting questions and not all questions being answered which was the case in Costa. The case of Costa v ENEL showed a conflict between a Treaty provision and also an Italian Statute privatising the company of which the defendant Costa was an investor. But at the time the Italian Law was at a later time than the treaty provision. In protest he refused to pay the bill which equated to Â£1.10 in English currency. Costa argued that the company was in breach of EU law. The defendants argued â€œLex posterior; the Italian act nationalising the electricity company was later in time than the Italian Ratification Actâ€. [Page 82 EU Law, Steiner & Woods]. This was an Act which incorporated EU law with Italian Law. From thereon the Italian Court was obliged to absolve the national law in preference with EU law. The Italian court referred this matter to the CJEU. The Magistrates Court also referred the matter to the Italian Constitutional Court. The CJEU came to these conclusions which was to spilt the two arguments into two main groups.; those relating to the nature of the Union and those relating to the purpose of the Union. The Court had ruled partly in favour of the Italian government because of the Treaty of Rome rule on a factual market, this means that the Commission can challenge independently the Italian government. As Costa was an individual he didnâ€™t have a legal standing to challenge that Treaty provision so it did not have direct effect. But as Costa rose a point of EC law against the national government in legal proceedings in the MS, the CJEU was against the views of the Italian government. The CJEU ruled that EC law would not be operative if Costa couldnâ€™t challenge the national law on the foundation of its alleged inconsistency with EC law. Inside the time period of the referral to the CJEU the principle of Supremacy was clearly affirmed as cited by the first case Van Gend En Loos, to show supremacy but was not enforced until the ruling in Costa. From Van Gend the MSâ€™s had â€˜limited their sovereign rightsâ€™ [judgment of Costa]. The CJEU went further on and looked at the Treaty under Article 288 which indicated that there had been a transmission of powers to the Union Institutions as Article 4 (3) states MSâ€™s commitment to observe union law. This shows the outcome of the case as the CJEU commented saying that national law should prevail over the earlier EU law. It was also noted by the CJEU Article 189 indicated a transfer of powers to Community Institutions. Under Article 5 it â€˜commits to observe EC lawâ€™. The CJEU said that â€œthe transfer of the States from their domestic legal system to the Community legal system to the Community legal system of the rights and obligations arising under the Treaty carries with it a permanent limitation of their sovereign rights. against which a subsequent unilateral act incompatible with the concept of the Community cannot prevailâ€. Further on it was stated that Community law would be deprived of its character which the legal forum of the community would be held for questioning if other MSâ€™s could introduce national laws which had supremacy over Community Law. Finally, the CJEU overturned the Italian decision in Costa as it was established that MSâ€™s could not diverge from Community treaties without prior authorisation, the high courts would have to consult the CJEU before deciding an incompatibility between MS and EC law. The case set an central precedent for the supremacy of Community Law within the European Community and later the EU. The prevalent principle established from Costa is the enforcement of Supremacy, this means that EU law prevails over any conflicting provisions of national law and take precedence over national law if they have â€˜direct effectâ€™ [Europa.eu]. This shows that the preliminary reference procedure was now in full force and had to be applied in every state of Europe. It has shown effect in other cases such as Simmenthal â€œthe full effectiveness of Community law would be impaired if a rule of national law could prevent a court from granting interim reliefâ€ [EU Law Steiner & Woods]. Furthermore, the significance of the case as seen through the judgement provided two main outcomes to the case as seen earlier. It created a new legal order of an independent nature which limited the MSâ€™s sovereign rights permanently, but in the Treaty there is no legal basis about this point. However, this shows that purpose of the Union and goals achieved will not be undermined., and also shows how EU law has become more effective. The effectiveness now becomes an element of the CJEU views and is rational which makes for a vast sway on the expansion of Union Law. Also, without the judgement in Costa, Community Law would fail to exist as it would be referred to as international law. Not until the time of the doctrine of supremacy did community law become truly â€˜supranationalâ€™ as was intended by the European Treaties. In the case of Costa v ENEL CJEU entered the political stage as the Court replaced the ruling of modus â€˜political integrationâ€™ with modus of â€˜legal integrationâ€™ [Article: on the Importance of Contemporary Statement of Legal History]. Although, the Supremacy has found difficulty after the Lisbon Treaty to fit in to all pillars of EU law. But the effects of the argument due to costa apply equally in the Community pillar. In addition, the significance of the case has changed Europe as supremacy is evolving; the enlargement of the EU has given a new dimension to the supremacy debate in Europe. Constitutional courts of Central Eastern Europe Countries are elaborating their own doctrine on issues of relation between EU law and National law with special regard to National Constitutional provisions. Above all, the ratification process of EU constitutions is contributing to supremacy debate in the EU. Recent jurisprudence of Spanish and French Courtâ€™s make a new primacy clause through supremacy and discussed a new structure of the constitutional treaty. The supremacy of EU is still an evolving and debating concept which has been given a new dimension through codification of Articles 1-6 of the EU constitution and jurisprudence of constitutional courts of the MSâ€™s, this shows rapid development of the EU due to Costa.