6.3 The principle of direct effect
Does the principle of supremacy of EU law mean that the ECJ is the only court in charge of applying and enforcing EU law? The answer to this question is ‘no’, which is the consequence of the principle of direct effect. Certain provisions of EU law may confer rights or impose obligations on individuals that national courts are bound to recognise and enforce. This means that the national courts must apply the directly applicable EU rules and must do so in priority over any conflicting provisions of national law. The scope of this principle has been gradually strengthened and extended to the point that now it applies to most secondary legislation. Also, many of the provisions of the treaties have been established as having direct effect.
Does the principle of supremacy together with the principle of direct effect mean that any EU rule should prevail over the national law? The answer is, again, ‘no’, due to two other principles governing the relationship between EU law and national law: proportionality and subsidiarity.