The Principle of Sincere Cooperation (Article 4(3) TEU)

The principle of sincere cooperation, also referred to as loyal cooperation or federal loyalty, is a foundational constitutional principle of EU law, now codified in Article 4(3) TEU. The principle imposes mutual duties of cooperation between the European Union and the Member States and among the Member States themselves. It requires Member States to take all appropriate measures to ensure fulfilment of their obligations under the Treaties, to facilitate the achievement of the Union’s tasks, and to refrain from any measure which could jeopardise the attainment of the Union’s objectives. The principle operates as both a constraint on Member State action and a source of positive obligations to act, and has been central to the constitutional development of the EU legal order.

Treaty Basis: Article 4(3) TEU

Article 4(3) TEU provides: “Pursuant to the principle of sincere cooperation, the Union and the Member States shall, in full mutual respect, assist each other in carrying out tasks which flow from the Treaties.” The Article specifies that Member States shall take any appropriate measure, general or particular, to ensure fulfilment of the obligations arising out of the Treaties or resulting from the acts of the institutions of the Union, and shall facilitate the achievement of the Union’s tasks. Member States shall refrain from any measure which could jeopardise the attainment of the Union’s objectives.

The principle operates in three dimensions. First, the vertical dimension governs the relationship between the EU and the Member States, imposing duties on both sides. Second, the horizontal dimension governs relations among Member States, requiring them to cooperate in good faith in matters of common concern. Third, the principle has been applied to the relations among EU institutions themselves, requiring inter-institutional cooperation in the exercise of their respective powers.

The ERTA Case and External Relations

The principle of sincere cooperation has particular significance in the field of external relations. In Commission v Council (Case 22/70), the European Road Transport Agreement (ERTA) case, the Court of Justice held that where the EU has exercised its internal competence in a particular area, Member States may not enter into international commitments that affect common rules or alter their scope. The case concerned the negotiation and conclusion of the European Road Transport Agreement (AETR/ERTA) by the Council while the Commission was also involved in parallel negotiations. The Court held that the competence to conclude the agreement derived from the implied external competence arising from the adoption of internal transport legislation, and that Member States were obliged to cooperate with the Commission in the negotiation process.

The ERTA judgment established the doctrine of implied external competence, based in part on the duty of loyal cooperation. Where the Union has adopted common rules in a given area, Member States may not individually or collectively enter into external commitments that affect those rules. The Court has subsequently applied the principle to require Member States to refrain from signing or ratifying international agreements that could affect EU law, even where the EU has not formally exercised its external competence.

Obligations of Member States

The principle of sincere cooperation imposes both positive and negative obligations on Member States. Positive obligations include: the duty to implement and enforce EU law effectively, including through the imposition of effective, proportionate, and dissuasive penalties for breaches of EU law; the duty to transpose directives correctly and within the transposition period; the duty to provide information to the Commission in infringement proceedings; and the duty to cooperate in the preliminary reference procedure under Article 267 TFEU.

Negative obligations include: the duty to refrain from adopting national measures that could compromise the attainment of EU objectives; the duty to refrain from negotiating, signing, or ratifying international agreements that could affect EU law; and the duty to refrain from creating obstacles to the effective application of EU law. The principle has been applied to prevent Member States from adopting national procedural rules that make the exercise of EU law rights excessively difficult or impossible — the principle of effectiveness (effet utile), which the Court has derived in part from the duty of sincere cooperation.

Application in the Area of Freedom, Security and Justice

The principle of sincere cooperation has been extended to the Area of Freedom, Security and Justice (AFSJ) . In the context of the Common European Asylum System, the Court has held in N.S. v Secretary of State for the Home Department (Cases C-411/10 and C-493/10) that Member States cannot transfer an asylum seeker to the Member State responsible under the Dublin Regulation where there are substantial grounds for believing that systemic deficiencies in the asylum system would expose the applicant to a real risk of inhuman or degrading treatment, contrary to Article 4 of the Charter of Fundamental Rights. The Court derived this obligation from the principle of sincere cooperation: Member States exercising their powers under the Dublin Regulation must respect fundamental rights and must cooperate with each other to ensure that the objectives of the Common European Asylum System are achieved.

Sincere Cooperation in CFSP

The principle also applies in the Common Foreign and Security Policy (CFSP) , though in a modified form reflecting the intergovernmental character of CFSP cooperation. Article 24(3) TEU provides that Member States shall support the Union’s external and security policy actively and unreservedly in a spirit of loyalty and mutual solidarity and shall comply with the Union’s action in this area. The Court has held in H v Council (Case C-455/14 P) that the duty of sincere cooperation in CFSP is binding on the institutions and the Member States, though the Court’s jurisdiction over CFSP matters is limited by Article 275 TFEU.