Application of EU law by the domestic Judge
Consistent interpretation
The effective application of EU law cannot be ensured by the EU and its courts alone. It depends strongly on domestic courts and individuals that initiate proceedings before these courts to enforce their rights under EU law. (Case 26/62 Van Gend & Loos [1963] ECR 1.)
Consistent interpretation
EU law must be applied by the domestic judge because it enjoys precedence over internal law. (Case 6/64 Costa v Enel; Case C 409/06 Winner Wetten, para. 53). National courts are, therefore, required to interpret their national law, to the greatest extent possible, in conformity with the requirements of EU law. This may even result into the change of established case-law, where necessary, if it is based on an interpretation of domestic law that is incompatible with the objectives of a directive (Case C-441/14 DI, para 33).
The meaning and scope of terms for which EU provides no definition must be determined by considering their usual meaning in everyday language, while also taking into account the context in which they occur and the purposes of the rules of which they are part (Case C-184/14 A, para. 32).
In Case C-585/10 Møller, the CJEU noticed that the term 'sow' does not have a univocal meaning in all the official languages. It decided for interpretation which equates gilts with the sows because, for industrial installations which have a significant potential for pollution, both sows and gilts have the same effect on the environment.
The CJEU generally favours giving an autonomous interpretation to concepts used in EU measures, with some exceptions when the Member States enjoy certain discretion (Case C-81/96 Gedeputeerde Staten van Noord-Holland, on the question of when a development consent is granted). Nevertheless, as regarding the purposes of the rules and the general scheme of environmental protection, any derogations must be interpreted strictly, both in national and EU law.
The interpretation of derogations from nature protection advocated by the CJEU is deliberately restrictive (See Case C-304/05 Commission v. Italy, para. 82). The CJEU even calls for 'faithful transposition', which is a term it uses exclusively in this respect and never in regards to other fields of EU law (for the Birds Directive, See Case C-38/99 Commission v. France, para. 53; for the Habitats Directive, Case C-6/04, Commission v. United Kingdom, para. 256). Similarly, in Case C-304/15 Commission v United Kingdom, the CJEU interpreted strictly condition for large combustion plants to qualify for derogation, because such interpretation was supported by the context of the particular footnote and by the objective of Directive.
While the principle of interpreting national law in conformity with EU law has certain limits and, in particular, cannot serve as the basis for an interpretation of national law contra legem, it nevertheless requires, to the greatest extent possible, that the whole body of domestic law is taken into consideration, and that the interpretative methods recognised by domestic law are applied, with a view to ensuring that EU law is fully effective, and achieving an outcome that is consistent with the objective it pursues. In short, the interpretation also has to ensure that EU law is fully effective (Case C-573/17 Poplawski, para 53-55).
In Case C-167/17 Klohn, the CJEU concluded that the Member States are required to interpret national law to the fullest extent possible, in such a way that persons should not be prevented from seeking, or pursuing a claim for, a review by the courts in environmental matters by reason of the financial burden that might arise as a result.