Short answer
National courts must use every interpretive method recognised by domestic law, considering the legal system as a whole, to reach a result consistent with an applicable EU directive. The duty can require a court to reconsider settled case law, and it applies whether the national provision was enacted before or after the directive.
The limit is that interpretation must remain interpretation. EU law does not require a reading that is contra legem—contrary to what the domestic law can bear under recognised methods. Legal certainty and non-retroactivity are further limits, especially where a new reading would create or aggravate criminal liability. If no conforming interpretation is possible in a dispute between private parties, the directive cannot by itself impose an obligation on the defendant.
National constitutional courts reserve exceptional controls based on conferred powers, constitutional identity and legality. These differ from ordinary contra legem analysis and normally involve preliminary-ruling dialogue with the Court of Justice of the European Union (CJEU).
Why national courts have this duty
Article 288 of the Treaty on the Functioning of the European Union (TFEU) explains the structure of a directive:
A directive shall be binding, as to the result to be achieved, upon each Member State to which it is addressed, but shall leave to the national authorities the choice of form and methods. —
That obligation binds every Member State authority within its jurisdiction, including courts. Consistent interpretation helps achieve the directive's result without pretending that the directive is itself a national statute.
In Marleasing, Case C-106/89, the Court of Justice made clear that the duty is not confined to legislation enacted to transpose the directive:
It follows that, in applying national law, whether the provisions in question were adopted before or after the directive, the national court called upon to interpret it is required to do so, as far as possible, in the light of the wording and the purpose of the directive in order to achieve the result pursued by the latter and thereby comply with the third paragraph of Article 189 of the Treaty. —
The court must examine the whole body of domestic law
Consistent interpretation is broader than choosing the EU-friendly meaning of one ambiguous sentence. In Pfeiffer and Others, Joined Cases C-397/01 to C-403/01, the Grand Chamber required the court to consider the whole body of domestic law and its recognised interpretive methods. Those can include reading provisions together, applying domestic priority rules, restricting a provision's scope, or revisiting a judicial construction.
In Dansk Industri (Ajos), Case C-441/14, the CJEU held that a court may have to change established case law where it defeats a directive's objective. A court cannot establish impossibility merely by saying it has always read the statute differently.
Adeneler and Others, Case C-212/04, distinguishes two periods:
- after the transposition deadline, the full duty of conforming interpretation applies;
- between the directive's entry into force and that deadline, national courts must, as far as possible, avoid readings liable seriously to compromise the result that must be achieved once the deadline expires.
The outer limit is contra legem
The CJEU does not define contra legem as a freestanding European test detached from national law. The national court must identify the interpretive methods its legal order recognises and test the whole domestic framework. But the final reading must remain available under those methods.
Adeneler states the limit directly:
It is true that the obligation on a national court to refer to the content of a directive when interpreting and applying the relevant rules of domestic law is limited by general principles of law, particularly those of legal certainty and non-retroactivity, and that obligation cannot serve as the basis for an interpretation of national law contra legem. —
The boundary is clearest where a proposed reading would contradict unambiguous statutory text and structure rather than correct an old judicial gloss. It is especially strict in criminal law: a directive alone cannot determine or retrospectively aggravate an individual's criminal liability.
A directive still cannot create a private obligation by itself
The duty of interpretation must not be confused with horizontal direct effect. In Dominguez, Case C-282/10, the Court required the French court to examine the whole body of labour law to see whether a directive-consistent reading was possible. If it was not, the court then had to ask whether the employer's legal nature made it an emanation of the State. If the employer was genuinely private, the directive could not itself resolve the dispute against it.
The Grand Chamber restated the point in Popławski II, Case C-573/17:
In addition, according to settled case-law, a directive cannot of itself impose obligations on an individual and cannot therefore be relied on as such against that individual before a national court. —
The Grand Chamber confirmed in Thelen Technopark, Case C-261/20, that primacy does not erase this distinction. Even a clear, precise and unconditional directive provision cannot support disapplication in a private dispute where that would impose an additional obligation on an individual. State liability may instead provide compensation.
Another EU rule can change the result. In the CJEU's Ajos judgment, disapplication rested on the general EU principle prohibiting age discrimination, not horizontal direct effect of Directive 2000/78/EC. The distinction matters whenever a Charter right or general principle accompanies a directive.
What national apex and constitutional courts have added
The Danish Ajos litigation exposed a direct disagreement. After the CJEU's preliminary ruling, the Danish Supreme Court concluded that the statutory wording, legislative history, and prior decisions left no interpretive route consistent with Directive 2000/78. It also held, by an eight-to-one majority, that Denmark's Accession Act did not authorise an unwritten EU principle to override the statute in a private dispute. The claim against the employer was dismissed.
In view of the foregoing, the Supreme Court takes the view that the state of the law is clear and that it is not possible, in applying the rules of interpretation recognised under Danish law, to arrive at an interpretation of Paragraph 2a(3) of the Law on salaried employees as then in force in a manner that is consistent with the Employment Directive as interpreted by the EU Court of Justice. —
That judgment illustrates both contra legem and a separate constitutional conflict over transferred powers. It is not an exception endorsed by the CJEU.
Germany's Federal Constitutional Court took a more restrained approach in Honeywell, 2 BvR 2661/06. It reserved ultra vires review for a manifest competence excess causing a structurally significant shift in powers. It required a prior opportunity for the CJEU to decide the EU-law issue, allowed the CJEU a margin of error, and rejected the challenge to the age-discrimination case law.
The Italian Taricco litigation shows judicial dialogue in practice. The Constitutional Court warned that retroactively extending criminal limitation periods could violate legality, then made a preliminary reference. In M.A.S. and M.B., Case C-42/17, the CJEU held that national law need not be disapplied where that would breach precision or non-retroactivity protected by Article 49 of the Charter and common constitutional traditions.
That case concerned Article 325 TFEU rather than a directive. Its relevance is methodological: constitutional objections do not automatically license a national court to redefine EU law. The preliminary-ruling process can identify whether the apparent conflict is resolved within EU law itself.
Questions for a national court
A disciplined analysis asks:
- Has the transposition deadline expired, and which version governed the facts?
- Which national rules and recognised interpretive methods bear on the issue?
- Would the proposed reading contradict statutory text and structure, or only depart from settled case law?
- Would it undermine legal certainty or retrospectively aggravate criminal liability?
- Is the defendant the State or a private party, and is another directly effective EU rule engaged?
- If a constitutional competence or identity issue remains, has the CJEU had an opportunity to address it?
Conclusion
National courts must work hard, and across the whole domestic legal system, to interpret national law consistently with an EU directive. They may need to abandon settled case law, but they need not—and may not—turn interpretation into legislation.
The boundary is contra legem, reinforced by legal certainty and non-retroactivity. A directive cannot itself supply a private obligation that interpretation cannot produce. Exceptional constitutional controls remain contested and closely tied to prior dialogue with the CJEU.
Sources
This article provides general legal information, not advice for a specific matter. Laws, facts and procedural deadlines may change the result. Follow the linked primary sources and obtain local advice before acting.