United Kingdom joined the European Community
Two principles which give effect for Community law within UK are S2 (1) and S2 (4) of the European Communities Act 1972. Section2 (1) states that the UK, must, for example enforce all rights directly resulting from the treaties and Community without further enactment to be given legal effect or used is directly enforceable in UK courts. Section2 (4) of European Communities Act 1972 provides that English law should be interpreted and have effect subject to the principle that European is supreme, this means that European law now takes precedence over all domestic sources of law. The words of S2 (4) are both retrospective and prospective  : “…any enactment passed or to be passed …shall be construed and have effect subject to the foregoing provisions of this section" This means that when domestic law conflicts with directly effective Community law, the latter must be applied and the only way not to follow the Community law is to repeal this subsection. Moreover, under section 3 of the European Communities Act 1972, the interpretation of Community treaties and legislation is regarded as question of law to be interpreted European Court of Justice if it is decided by the courts of the UK; the matter is decided in accordance with ECJ decisions.
There are four different types of Community law- treaties, regulations, directives and decisions. Article 10 (5) of the Treaty obliges all Member State to take all appropriate measures, whether general or particular, to ensure fulfillment of all these obligations. All member states, include UK, are imposed to apply community obligations through the English and Welsh court. The law-making power of the Community institutions is laid down in Article 249 of European Community Treaty. Under Article 249 of European Community, a regulation will be general applicable and normally directly applicable to all member states. The ECJ has held that both treaties and regulations can give rise to direct effect. Where a provision of European Community law is describe as giving rise to direct effect, it means that it can be invoked by an European Union citizen against an European Union member state in the domestic courts of that state.
Community laws forms part of the national law of every member state.
The European Court of Justice (ECJ) has held that Community law prevails over national law if there is conflict between them from both treaties and statement made by ECJ. Section 3 bind all UK courts to interpret matters of Community law in accordance with the rulings of ECJ and requires the courts to take judicial notice of Community legislation and the opinions of the ECJ. Section3 (1) also states that the UK Parliament has given a duty and power to the UK courts to help the UK carry out its treaty obligations and in doing so, UK Parliament intended the courts to apply Community law, in the event of a conflict between Community law and an Act of Parliament.  It means that the courts are under a duty to give priority to Community law over inconsistent UK legislation and the duty is imposed by the European Communities Act 1972. Under Article 220 of European Community Treaty, the task if the Court is to ensure that in the interpretation and application of this Treaty, the law is observed. It is the supreme authority on all matters of Community law. The ECJ is the judicial arm of the European Union and in the field of the Community law its judgments overrule those of national courts. Under Article 234, national courts have the right to apply ECJ for a preliminary ruling on a point of Community law before deciding a case as the crucial wordings in the article- “the Court of Justice shall have jurisdiction to give preliminary rulings concerning":
interpretation of this Treaty
the validity and interpretation of acts of the institutions if the Community and of the ECB
the interpretation of the statues of bodies established by an act if the Council; where those statues so provide
The primary function of the ECJ is to ensure that the provisions of various treaties which create by European Union are applied properly by the member states. Clearly, large-scale failure by a member state to comply with the requirements of European Community law would be raised by the European Commission, or other member states. On the other hand, there has been a change to the doctrine of parliamentary sovereignty as there is now exists a legislative body which can create law for the judges to interpret and will normally give precedence to it over domestic law.
In the case R v Secretary of State for Transport, ex parte Factortame (No. 2)  AC 603, litigation begin because of a dispute over fishing rights in British coastal waters. The Common Market Fishing Policy devised a system to conserve fish by fixing quotas for national fishing fleets. The British government established a licensing system in 1985 which was expanded upon in the Merchant Shipping Act 1988 and which empowered the Secretary for Transport to make regulations and introduce a new register of British fishing vessels designed to prevent so-called “quota hoping". By the late 1980s, some vessels owned by Spanish companies had done so, by establishing companies in the UK in order to avail themselves of the British fishing quota. Factortame which was affected by the Merchant Shipping Act 1988 subsequently launched an action in the British courts claiming that the Merchant Shipping Act 1988 was substantively incompatible with European Community law. The Court of Appeal set aside the order for injunction and later Factortame appealed to the House of Lords. The court granted temporary injunctive relief suspending those parts of the Merchant Shipping Act 1988 which were in conflict with Community law. A reference to the ECJ under Article 234 of European Community, the House of Lords accord precedence of European Community law and eventually ruled that the Merchant Shipping Act 1988 breached the European Community law and thus domestic courts were required to give effect to directly enforceable provisions of Community law. The UK courts are subjected to the supervisory jurisdiction of the ECJ, as explained, and this give a further source of law, since the courts of all member states are bound by ECJ decisions on the interpretation and application of European Union law. The approach is not consistent with the traditional UK doctrine of the sovereignty of Parliament. However, we can see clearly from the case that how UK courts would act if faced Act of Parliament emerge conflict with Community law. In this case, the court added that national courts must be capable of protecting claimed Community law rights in the face of clear contrary provisions in national law, pending the ECJ’s final ruling on the precise nature of those rights. 
According to AV Dicey’s theory of parliamentary sovereignty, no parliament may be bound by a predecessor or bind a successor. A subsequent Act of Parliament may express or impliedly repeal any previous legislation. Doctrine of implied repeal provides that an earlier Act of Parliament may be impliedly repeal by the subsequent of a provision made by Parliament which is not consistent with the earlier one, it means that the earlier one is void. The European Communities Act 1972 does not expressly deal with the issue of parliamentary sovereignty, but provisions is made in S2 (4) which states “any domestic legislation enacted after 1972 will be construed and have effect subject to" European Community law. It means that where domestic legislation passed after 1972 is in conflict with Community law, the doctrine of implied repeal cannot apply.
To conclude, it can be seen through the concepts such as direct applicability, direct effect, indirect effect and damages for non-compliance, the ECJ has truly fulfilled a dynamic role in ensuring that the courts of all member states are have obligations to give primacy to European Community law.