In England, an archetypal country of common law, there is a hierarchy of sources as follows:[2] In addition to the general conditions of direct effect, the “formal source of law in which the EU legal norm is contained” also plays a role in the direct effect of a provision (Witte 2011, 333). In Article 288 TFEU, the EU defined the secondary sources of EU law, namely regulations, directives, decisions, recommendations and opinions (Mittwoch 2013, 13). Although regulations and decisions have a direct effect, the guidelines are different (Craig and de Búrca 2015, 200). This becomes evident when looking at the definition of directives: they are addressed to Member States, they are “binding in relation to the objective to be achieved” and they leave the method to achieve the objective to the Member States (Craig and de Búrca 2015, 108). In addition, a directive must be properly implemented by EU states within the prescribed timeframe (Dougan 2011, 413). Therefore, although directives do not always fulfil the three conditions of direct effect (clarity, precision and unconditionality), the CJEU has nevertheless ruled that directives can have direct effect (Craig and de Búrca 2015, 201). However, as we shall see below, the case-law of the CJEU on directives comes up against a tension between two objectives: the objective of ensuring the effectiveness of EU law and its uniform application between Member States, and of preserving “the specific identity of directives as a form of indirect legislation” (Dashwood 2006/07, 82). Compared to other sources of law, precedents have the advantage of flexibility and adaptability and may allow a judge to apply “justice” instead of “the law.” In civil law systems, sources of law include legal systems such as the Civil Code or the Penal Code and customary law; [Note 2] In common law systems, there are also several sources that merge to form “The Law”. Civil law systems often adopt common law ideas[note 3] and vice versa.

Scotland, for example, has a hybrid legal form, as does South Africa, whose law is an amalgam of common law, civil law and tribal law. For decades and centuries, legal principles have been derived from customs. The divine right of kings, natural and legal rights, human rights, civil rights, and common law are the earliest unwritten sources of law. Canon law and other forms of religious law form the basis of law derived from religious practices and teachings or sacred texts; This source of law is important if there is a state religion. Historical or judicial precedents and jurisprudence may modify, or even create, a source of law. Laws, rules and regulations are the tangible source of codified and enforceable laws. As regards the application of the principle of direct effect, legal writers generally refer to `any binding Union law, including the Treaties, the Charter of Fundamental Rights, general principles, secondary legislation and international agreements` (Craig and de Búrca 2015, 184). As regards the primary sources of EU law, namely the EU Treaties and the Charter, this paper focuses on the former. The reason for this is that in 1963, the ECJ in the famous Van Gen den Loos case, Case 26/62, NV Algemene Transporten Expeditie Onderneming van Gend en Loos v Nederlandse Administratie der Belastingen (1963), ECR 26/62, NV Algemene Transporten Expeditie Onderneming van Gend en Loos v Nederlandse Administratie der Belastingen (1963), ECR 26/62.

In 1963 it first expressed the doctrine of direct effect by declaring that Article 12 of the EEC Treaty had direct effect. the “most famous of all decisions” (Craig and de Búrca 2015, 187). The case concerned a Dutch company importing chemicals from Germany to the Netherlands and stated that the Netherlands tax authorities had imposed increased duties on its products, in breach of Article 12 of the EEC Treaty (now Article 30 TFEU) (Craig and de Búrca 2015, 187). The present case is an example of vertical direct effect, since Van Gend en Loos, as an individual, challenged an authority of the Netherlands State. The Court established the principle of direct effect by stating that the EEC establishes a `new legal order of international law` which concerns not only Member States but also individuals and not only imposes obligations, but also confers on individuals rights `forming part of their legal heritage` (Union a). Those assertions imply that the direct effect of EU law is an `inherent feature` of Community law (Reinisch 2012, 59). This is supported by the fact that the wording of the doctrine is addressed not only to the Dutch tax authority, but to all courts in all EU Member States (Witte 2011, 326). And in this particular case, the Court held that Art.

12 because it contains a `clear and unconditional prohibition`, is `ideally suited to produce direct effects in legal relations between the Member States and their subjects` (EU a) and has confirmed that the article produces its effects directly in a vertical case. The CJEU concluded that, by virtue of “the spirit, general scheme and wording of the Treaty, Article 12 must be interpreted as having direct effects and creating individual rights which national courts must protect” (Union a). The article focuses first on the direct effect of EU primary law, in particular the articles of the Treaty, before addressing the principle of secondary sources, in particular directives. It then examines the strategies developed by the CJEU to neutralise the effects of the rule that directives do not have horizontal direct effect, leading to the conclusion that indirect effect becomes less relevant. In the Member States, EU law is generally `applied and applied in a decentralised manner by national authorities` (Reinisch 2012, 58). In this context, the Court of Justice of the European Union (CJEU) has increased the effectiveness of EU law by extending the notion of direct effect to primary sources such as Treaty provisions and to secondary origins of EU law such as regulations and, in exceptions, directives (Reinisch 2012, 58).