Addicted to Exclusivity in EU External Action: Another Chapter in Constitutionalising the Unity of EU Representation in International Fora. Case C-271/23 [GC], European Commission v Hungary (Reclassification of Cannabis)

Table of Contents: 1. Introduction. – 2. Factual and legal background. – 3. Preliminary issues: admissibility. – 4. Assessment and findings of the CJEU. – 4.1. Breaching the Council decision setting out the common EU position. – 4.2. Disrespecting the EU’s exclusive external competence under Article 3(2) TFEU. – 4.3. Breaching the principle of sincere cooperation (Article 4(3) TEU). – 5. Analysis. – 5.1. Countering contra legem Member State action by mobilising firm constitutional reasoning. – 5.2. Beyond ERTA: Lowering the bar for EU exclusive competence in external relations. – 5.3. Further emancipating the duty of sincere cooperation: a structural principle with ever-sharper teeth in EU external action. – 6. Conclusions.

Abstract: The unity of European Union (EU) external action has been repeatedly tested in recent years, with Hungary frequently obstructing common EU positions in international fora. This case note examines the January 2026 Grand Chamber judgment of the Court of Justice of the EU (CJEU) in Commission v Hungary (Reclassification of cannabis) (Case C-271/23), in which the CJEU addressed one such disruption within a multilateral setting – the United Nations (UN) Commission on Narcotic Drugs. Arising from an Article 258 TFEU infringement action, the case turned on whether an EU Member State may ‘break free’ and vote against a common EU position on the ground that it considers that position unlawful. The European Commission contended that Hungary’s departure from Council Decision (EU) 2021/3 – fixing the Union's position on the scheduling of cannabis and related substances under two UN drug-control conventions – infringed both the EU’s exclusive external competence (Article 3(2) TFEU) and the duty of sincere cooperation (Article 4(3) TEU). The CJEU agreed on every count. Through an expansive construction of EU exclusive external competence and a robust, stand-alone application of the constitutional principle of sincere cooperation, the CJEU reinforced the unity of EU external action while sharply curtailing Member States’ room to act unilaterally in international fora – even in those the EU cannot formally join. This Grand Chamber ruling promises greater discipline and consistency in EU external action; yet risks chilling dissent on sensitive matters. Ultimately, it stands as a significant brick in the increasingly constitutional edifice of EU external relations law.

Keywords: EU external action – UN conventions on drugs control – Framework Decision 2004/757/JHA – common EU position under Article 218(9) TFEU – EU exclusive competence – principle of sincere cooperation. 

1.   Introduction

The unity of representation of the European Union (EU) in its external action has been facing some significant challenges over the past years. One Member State that has regularly obstructed the adoption of common EU positions or undermined taking common (external) action in unity was Hungary.[1] A demonstrative example of blocking the EU speaking in one voice on the international plane is voting against the EU’s common position represented in international organisations and other multilateral fora.

The Grand Chamber judgment of the Court of Justice of the European Union (hereinafter: ‘CJEU’ or ‘EU Court’) in Commission v. Hungary (Reclassification of cannabis) (Case C-271/23), delivered on 27 January 2026,[2] dealt with such a situation when one Member State, Hungary disrupted the unity of EU external action in a multilateral forum, namely the United Nations (UN) Commission on Narcotic Drugs (CND).[3] The case before the CJEU originated from an infringement procedure initiated by the European Commission (Commission) under Article 258 of the Treaty on the Functioning of the European Union (TFEU). 

The Commission claimed that Hungary had failed to fulfil its obligations stemming from a Council decision establishing the position to be taken, on behalf of the EU, by Member States in the CND when voting on the reclassification of cannabis and cannabis-related substances under two international drug-control conventions.[4] By doing so, Hungary has also disrespected the EU’s exclusive external competence under Article 3(2) TFEU and the fundamental principle of sincere cooperation set out in Article 4(3) of the Treaty in European Union (TEU); the Commission also submitted. Hungary, in defence, alleged that the Council decision was unlawful. Accordingly, the central question in the present legal dispute was whether an EU Member State may ‘break free’ and vote against an EU common position in the CND on the grounds that it considers that position unlawful?

The CJEU, sitting in the Grand Chamber, upheld the Commission’s claims, finding that Hungary, by unilaterally departing from the common EU position set out in the aforementioned Council decision, had infringed EU law. In doing so, Hungary not only encroached upon the Union’s exclusive external competence in the area (drugs policy) but also violated the duty of loyal cooperation.

2.   Factual and legal background

The factual and legal background of this Grand Chamber ruling is essential to understand its broader significance. 

The point of departure lies in January 2019, when the World Health Organization (WHO), which is one of the 16 UN specialized agencies,[5] submitted six recommendations[6] to amend the classification of cannabis and cannabis-related substances under the two most important multilateral drug-control instruments drawn up under the UN aegis, namely the 1961 Convention on Narcotic Drugs[7] and the 1971 Convention on Psychotropic Substances.[8]

Although the EU is not a party to these conventions – all Member States are –, it has an observer status in the UN Commission on Narcotic Drugs. This UN body is composed of 53 UN member States which are selected by the UN Economic and Social Council (ECOSOC). At the time of dispute, 12 EU Member States – including Hungary – were members thereof with the right to vote.

In intra-EU fora, Member States discussed these 2019 WHO recommendations on several occasions within the competent preparatory body of the Council of the EU. The European Monitoring Centre for Drugs and Drug Addiction – replaced by the European Union Drugs Agency since then – also assessed the impact of those WHO recommendations. As a result of these intra-EU negotiations, the Council of the EU adopted a common position, in November 2020, on proposed changes to the scheduling of cannabis and cannabis-related substances within the above two UN conventions. Council Decision (EU) 2021/3 was adopted with qualified majority pursuant to Article 218(8)-(9) TFEU[9] – with Hungary voting against and Bulgaria abstaining. That decision was addressed to all EU Member States.

At the Union level, the objectives of the two UN drug-control conventions have been translated into the EU legal framework via Framework Decision 2004/757/JHA setting forth, as a form of minimum harmonisation, the constituent elements of criminal acts and penalties in the field of illicit drug trafficking.[10] Most notably, ‘drugs’ are defined, in Article 1(1), with reference to the two UN drug-control conventions. Also, the general penalties for crimes involving highly addictive drugs and the more specific penalties for crimes involving most harmful drugs and those not used for medical purposes follow the categorisations of the 1961 Convention on Narcotic Drugs (see its Schedules I and IV). 

Even though the EU is not itself a member of the UN Commission on Narcotic Drugs, where matters fall within EU competence or are otherwise coordinated at the Union level, Member States participating in the CND are expected to act collectively in accordance with EU-agreed positions. 

On 2 December 2020, a vote on the above-mentioned WHO recommendations took place within the CND at is 63rd session.[11]WHO Recommendation 5.1 – which advocated for removing cannabis or cannabis resin from a schedule to the 1961 Convention – was adopted, whereas Recommendations 5.2 to 5.6 were rejected. Hungary, one of the CND members at the time, chose to vote against the EU’s agreed position which supported all six WHO recommendations. It not only voted against Recommendations 5.1 (see above) and 5.4 (seeking to delete cannabis extracts and tinctures from a schedule to the 1961 Convention), but it also publicly stated within the CND that the adoption of these WHO recommendations would increase the already growing use of cannabis and would involve unjustified interference with its national policies.

This misaligned conduct prompted the European Commission to initiate infringement proceedings under Article 258 TFEU, arguing that Hungary i) failed to fulfil its obligations under Council Decision (EU) 2021/3; ii) infringed the EU’s exclusive external competence pursuant to Article 3(2) TFEU; and (iii) breached the duty of sincere cooperation enshrined in Article 4(3) TEU.

In the pre-litigation stage, Hungary pointed out that it has already expressed reservations about the WHO recommendations during the decision-making process in the Council which led to the adoption of Decision (EU) 2021/3. As a consequence of its dissatisfaction, driven by public health and social policy considerations, it voted against this Council decision. Given that Hungary maintained its position following the Commission’s reasoned opinion of January 2022 and the Commission remained unconvinced by the arguments put forward by the Hungarian government, the matter was ultimately referred to the EU Court in February 2023.[12]

3.   Preliminary issues: admissibility

In view of the multiple pleas of inadmissibility raised by Hungary, the CJEU first turned, as a preliminary matter, to examine those objections – and rejected them in a systematic manner, one by one. 

It began by dismissing Hungary’s contention that the Commission had failed to indicate the measures necessary to bring the alleged infringement to an end. In this regard, the CJEU reiterated – citing its well-established case law[13] – that, in infringement proceedings under Article 258 TFEU, the Commission is under no obligation to specify the corrective steps to be taken. The function of such proceedings is confined to securing a declaration that a breach of EU law has occurred. It is thus up to the Member State, under Article 260(1) TFEU, to take the necessary steps to comply with the judgment of declaratory nature.

Second, the CJEU rejected the claim that the alleged infringement could no longer be brought to an end or had no lasting effects. The Grand Chamber emphasised that a Member State cannot rely on the fact that an infringement has already produced its effects in order to evade judicial review before the EU Court. Accepting such an argument would undermine the Commission’s role as the ‘guardian of the EU Treaties’, the binding nature of EU decisions as per Article 288 TFEU, and more broadly, the respect of the EU values embodied in Article 2 TEU – one of which is the rule of law. Moreover, the effects of Hungary’s conduct were not confined to the specific vote but went beyond that specific decision-making process in the CND. They undercut the unity and consistency of the EU’s external action in a UN body – argued the Grand Chamber.

Third, the EU Court clarified that the admissibility of an infringement action does not depend on demonstrating a risk of repetitionof the alleged breach in the future.

Finally, the CJEU held that Hungary’s argument that it had no alternative but to depart from the common EU position relates to the substance of the case and is therefore irrelevant at the admissibility stage. This last plea was, therefore, joined to the in-merit examination of the claimed infringements.

4.   Assessment and findings of the CJEU

After determining that the case was admissible, the CJEU examined the three grounds of infringements the Commission submitted in relation to Hungary’s action in the UN Commission on Narcotic Drugs. The following briefly recaps, one by one, the EU Court’s key findings and the underlaying main arguments – starting with the most specific plea of law towards the more general ones.

4.1   Breaching the Council decision setting out the common EU position

Since Hungary’s key argument in this regard was that Council Decision (EU) 2021/3 was an unlawful act, the CJEU began by dealing with the applicability of the exception of illegality (Article 277 TFEU) in infringements proceedings (paragraphs 111–132). 

After recalling the fundamental distinction between infringement actions seeking a declaration that a Member State has failed to fulfil its obligations under EU law (Articles 258–259 TFEU) and actions for annulment seeking to invalidate an adopted piece of secondary EU legislation (Article 263 TFEU), the ruling made it clear: Member States cannot, in principle, invoke the illegality of an EU legal act adopted by the institutions as a defence in infringement proceedings concerning its failure to comply with that piece of EU law. The only exception arises where the legal act is vitiated by such particularly serious and manifest defects that it can be regarded as non-existent. This highly exceptional threshold was not met in the present case: Hungary did not demonstrate any defect capable of rendering the contested Council decision non-existent. 

The CJEU went on emphasising that Member States are required to challenge allegedly unlawful EU legal acts through an action for annulment within the prescribed time limits (two months from the measure’s date of publication). An infringement action cannot thus serve as a substitute for such a legal challenge, nor can it remedy a Member State’s failure to put in motion Article 263 TFEU in due time. Another option for Hungary would have been seeking the suspension of the Council decision pending review, in application of Article 278 TFEU and Article 160(1) of the Rules of Procedure of the CJEU[14] – this legal avenue has not been activated either.

In addition, the EU Court underscored the presumption of validity attached to EU legal acts, which obliges Member States to comply with them so long as they have not been annulled or suspended by the CJEU. If Member States were allowed to disregard such EU acts unilaterally and adopt, on their own, measures ‘to cure any breach [of EU law], by another Member State or by an EU institution’ (paragraph 126), that would undermine the uniform application of EU law. This is based on a well-established key structural principle of the EU legal order, namely that the EU Treaties ‘prohibit the Member States from taking the law into their own hands’ (paragraph 125), as the CJEU famously laid down back in 1964 in Commission v Luxembourg and Belgium (Joined Cases 90/63 and 91/63).[15] The EU Court opined: Member States breaking unilaterally, as they see fit as per their national interest, the balance of rights and obligations stemming from their EU membership calls into question the equality of Member States and is incompatible with the duty of solidarity, being one of the fundamental values the EU is founded on pursuant to Article 2 TEU.

Turning to the substantive assessment of whether Hungary infringed Council Decision (EU) 2021/3, the EU Court confirmed (paragraphs 133–138): that decision – adopted in accordance with the procedure laid down in Article 218(8)–(9) TFEU and within the scope of the Union’s (exclusive) competence under Article 3(2) TFEU (see below section 4.2) – constitutes a legally binding act establishing the common EU position within an international body. This is also due to the fact that, under Article 288 TFEU, a decision adopted by the EU institutions is intended to have legally binding effect in its entirety. Publishing the decision in the L series of the Official Journal of the EU as a legally binding act equally reflected that.

Against this backdrop and given that the EU had competence to adopt this decision which enjoys the presumption of validity, not acting in line with its content constitutes a breach of that legally binding act of the Council. 

4.2   Disrespecting the EU’s exclusive external competence under Article 3(2) TFEU 

Starting with a (preliminary) procedural point before going into the merits, the EU Court stressed: Article 218(9) TFEU applies irrespective of whether the Union’s external competence is exclusive or shared. It also confirmed its position established since Opinion 2/91[16] that even if the EU is not a member of an international organisation, this does not prevent its external competence from being exercised, particularly through Member States acting together in the EU’s interest.

It then recalled the conditions under Article 3(2) TFEU, according to which the Union acquires exclusive external competence where international obligations ‘may affect common rules or alter their scope.’ In that regard, the CJEU reiterated that such an effect may arise even in the absence of direct conflict, and even where the EU is not formally a member of the international organisation in question, provided that Member States participating in that international organisation act in the Union’s interest.

Applying those principles to the present dispute, the CJEU found (paragraphs 99–108): relying on the proposed amendments to the classification of cannabis and related substances under the two UN drug-control conventions was liable to affect the meaning,scope, and effectiveness of EU law, namely Framework Decision 2004/757/JHA. Because this piece of EU law defines ‘drugs’ by reference to the UN conventions (Article 1(1)) and relies on the latter’s schedules, any modification to these schedules would riskaffecting common EU rules. More concretely, deleting cannabis from the list of most harmful drugs (as per WHO Recommendation 5.1) and removing cannabis extracts and tinctures from the list of highly addictive drugs (as per WHO Recommendation 5.4) would alter the level of criminal penalties applicable under the Framework Decision (Article 4), or even exclude certain substances from the scope of those rules altogether.

In light of the foregoing, the EU Court concluded (paragraphs 109–110) that the proposed amendments suggested by WHO were capable of affecting common EU rules, thereby deciding on them in a UN body falls with the EU’s exclusive external competence as per Article 3(2) TFEU. Therefore, Hungary’s non-alignment with the common EU position during the vote in the CND encroached upon the Union’s exclusive competence in the field of drug control.

4.3   Breaching the principle of sincere cooperation (Article 4(3) TEU)

Here again the CJEU began by outlining the key requirements deriving from the principle of sincere cooperation (Article 4(3) TEU); recalling that this duty of crucial importance applies across all policy areas covered by the EU Treaties. It entails, in situations of shared competence between the EU and its Member States in external relations, an obligation of close cooperation between them throughout the negotiation, conclusion, and implementation of undertaken international obligations. This duty derives from the need to ensure the unity of the EU’s international representation, as the CJEU has recurrently underscored in its earlier case-law.[17]

In this context, the EU Court emphasised: Member States are subject to specific duties of action and abstention which preclude unilateral conduct in international bodies where a common EU strategy has been established. Any departure from such a strategy has multiple harmful effects: it undermines the unity and effectiveness of the EU’s external action, as well as its credibility and negotiating position vis-à-vis third partners. These obligations apply with particular force in areas falling within the EU’s exclusive external competence.

The CJEU further underlined that Member States must pursue their national interests within the institutional frameworkestablished by the EU Treaties, notably through collective deliberation in the Council, rather than through unilateral external action. Compliance with Council decisions adopted under Article 218(9) TFEU constitutes a specific expression of the requirement of unified external representation, arising from the duty of sincere cooperation under Article 4(3) TEU.

Applying these principles to the present case, the EU Court found that Hungary, by voting within the UN Commission on Narcotic Drugs contrary to the common EU position and by publicly expressing disagreement with the underlying WHO recommendations, had breached its duty of loyal cooperation under EU law. The CJEU also clarified that the isolated nature of the conduct or the absence of remedial measures was irrelevant to the finding of infringement.

5.   Analysis

Commission v Hungary (Reclassification of cannabis) is a peculiar case. It represents a microcosm of multiple key issues under EU external relations law and beyond. Although some scholars wondered about why this was a Grand Chamber case – other than to treat a Member State diplomatically[18] – the questions tackled therein are not merely technical and did not only warrant the mechanical application of already existing CJEU case-law on how to conduct EU external relations. The judgment touches upon fundamental issues of vertical division of competences between the EU and its Member States, the nature of the EU as an international (global) actor, and Member States’ sovereign prerogatives (and thus their retained margin of manoeuvre) in conducting international relations touching upon EU matters.

The ruling constitutes a significant development in the constitutional architecture of the EU’s external relations law, raising deeper questions about the trajectory of its constitutional centralisation. At its core, the case addresses the extent to which Member States remain autonomous actors in international organisations (even in those without the EU being a formal member)[19] once the EU has adopted a common position within the meaning of Article 218(9) TFEU – which is different from EU common positions adopted under the Common Foreign and Security Policy (Article 34 TEU).[20] The CJEU reaffirmed and arguably expanded the basic principles governing the unity of the Union’s external representation, the duty of sincere cooperation, and the scope of the Union’s (exclusive) external competences.

Zooming in on the concrete legal issues at stake, the CJEU found three breaches of EU law committed by Hungary. Moving from the specific to the general ones, these were i) violating the Council decision setting out the common EU position in the UN Commission on Narcotic Drugs; ii) disrespecting the EU’s exclusive external competence under Article 3(2) TFEU; and iii) breaching the principle of sincere cooperation (Article 4(3) TEU). These interrelated breaches of EU law can be seen as nested within one another, much like the layers of a Matryoshka doll.

5.1   Countering contra legem Member State action by mobilising firm constitutional reasoning

The least surprising finding concerns the confirmation that Hungary breached EU law by not aligning its action in the CND with Council Decision (EU) 2021/3, given that the latter is a decision as per Article 288 TFEU which must be given legally binding force in its entirety, and it was published in the L series of the Official Journal of the EU as a legally binding act. Pre-existing CJEU case law, cited in the ruling (paragraph 135), also confirms this position by pointing out that a decision adopted under Article 218(9) TFEU ‘is binding in nature […] with respect to the Member States inasmuch as it obliges them to defend that position’.[21] This has been consistently held by the EU Court irrespective of the political or technical nature of or the weight ascribed to the international body set up by a treaty – be it the Conference of the Parties to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES);[22] the International Organization for Vine and Wine (OIV);[23] or the Intergovernmental Organisation for International Carriage by Rail (OTIF).[24]

In this context, the plea of illegality raised by Hungary triggered even more noteworthy and far-reaching argumentation by the CJEU. The latter employed vigorous constitutional language to reject the alleged illegality of the Council decision, invoking a veritable ‘firework display’ of foundational constitutional concepts and structural principles of EU law (paragraphs 125–127). The non-permissibility of unilateral measures to enforce obligations under EU law (as a form of the exceptio non adimpleti contractus),[25] the equality of Member States (Article 4(2) TEU), the duty of solidarity between Member States (Article 2 TEU), and the principle of non-discrimination were all mobilised to dismiss Hungary’s argument challenging the legality of Council Decision (EU) 2021/3. Enough is enough – was the CJEU’s unmistakable message. All this clearly shows that the EU Court took up the gauntlet and deployed EU constitutional law’s heavy artillery against such brazen arguments that jeopardised the uniform application and enforcement of EU law. It was not the first time that Hungary’s manifest disregard of its core obligations stemming from EU primary law – with an attitude that seems almost provocative – prompted the judges in Luxembourg to employ fierce constitutional language when condemning such conduct and to recall the very basic foundations of the EU legal order and its cornerstone structural principles.[26]

Circling back to paragraph 125 of the present judgment, a remarkable half-sentence is hidden there which concerns the boundaries of the doctrine that the scheme of the EU Treaties ‘prohibits Member States from taking the law into their own hands’. The non-applicability, within the EU legal order, of the classic public international law principle of reciprocity, also known as the exceptio non adimpleti contractus,[27] does not appear to be absolute here. It is allowed ‘where expressly provided for’ under EU law – held the bench tout court. It remains to be seen which these cases may be, as the jurisprudence from Luxembourg has not unpacked that yet. Thus far, scholarly theorising has explored conceivable scenarios in which the enforcement mechanisms available under the EU legal order have been exhausted to no avail, such that the general rules of state responsibility[28] – including recourse to unilateral countermeasures – may exceptionally operate as a fallback (residual) option for Member States.[29] Overall, the CJEU has resoundingly shut many doors to forcefully protect the integrity of the EU legal order and its centralised enforcement scheme while also keeping one door slightly ajar – as a possible legal entry point or échappatoire for future nuancing its case-law.

5.2   Beyond ERTA: Lowering the bar for EU exclusive competence in external relations

When it comes to the finding that the EU enjoys exclusive external competence in the matter of classifying drugs and related substances, the CJEU left the safe port of its earlier jurisprudence and ended up being somewhat innovative. Although its reasoning builds upon the seminal ERTA judgment (Case 22/70)[30] – which established that the existence of internal EU competence precludes Member States from undertaking international commitments that affect common rules and alter their scope –, the EU Court essentially extended the ERTA logic beyond the conclusion of an international agreement to also encompass voting behaviour within international bodies, such as the UN Commission on Narcotic Drugs. Occupation of field or conflict pre-emption[31] have thus been put into motion, as specifically foreseen by the two scenarios covered in Article 3(2) TFEU and further elaborated in CJEU case law. The ruling thus contributes to the ongoing expansion of what might be described as ‘functional exclusivity’ in EU external relations law.

However, critics submit that elevating the mere ‘risk’ of affectation of common EU rules to the level of triggering exclusive EU competence in the case at hand sets aside the minimum harmonisation exception as a legal test in a situation where an EU instrument contains a reference to an international legal norm. The minimum harmonisation exception got first recognized in Opinion 2/91, meaning that the exclusive nature of EU external competence within the meaning of the last sentence of Article 3(2) TFEU does not arise where both EU law and the applicable international agreement only lay down minimum standards.[32] Although Hungary raised this argument, the EU Court simply set it aside as non-applicable (paragraph 108) and did not engage with the interpretation of allegedly minimum rules, unlike – as a commentator noted [33] –in Opinion 3/15[34] or Commission v Council (Neighbouring Rights).[35] Seemingly, the CJEU has moved away from applying the co-legislators’ intent in setting up a minimum harmonisation piece of EU law (here: Framework Decision 2004/757/JHA) towards the scope and nature of the common rules themselves.[36]

Assuming that the purpose of the minimum harmonisation exception is to leave untouched the level of harmonisation reached by the co-legislators, then it would have been perfectly reasonable to rely on this exception and not to resort to determining whether common EU rules are being affected by changes to the two UN drug-control conventions. The CJEU thus apparently pursued an approach where a mere risk of affectation or alteration of common rules suffices, without genuinely engaging with the minimum harmonisation exception and not considering the actual level of harmonisation of both the 2004 Framework Decision and the two UN drug-control conventions.[37] As mentioned above, Hungary’s argument in this regard was dismissed in a short sentence on the basis of the non-comparability of the factual background of this case and the situation in Opinion 2/91. The position taken by the CJEU therefore fits into the post-Lisbon jurisprudential line which lowered the threshold and simplified the assessment for finding an EU (external) competence exclusive,[38] hence widening the operational space for the conflict or obstacle pre-emption in the external dimension of EU action.

5.3   Further emancipating the duty of sincere cooperation: a structural principle with ever-sharper teeth in EU external action

Turning to the third, outer layer of this legal Matryoshka doll of violations, the EU Court relied heavily on the principle of sincere cooperation – the EU-law manifestation of the customary international law principles of pacta sunt servanda and good faith[39] – as yet another legal ground to establish that Hungary has failed to fulfil its obligations under EU law. Keeping with existing case-law, notably Commission v Greece (IMO),[40] the exclusive nature of the EU competence – confirmed in paragraphs 103–109 of the present ruling – was enough to pre-empt Member States’ independent action and activate the duty of sincere cooperation.

As well known, Article 4(3) TEU obliges Member States to ‘facilitate the achievement of the Union’s tasks’ and to refrain from measures that could jeopardise the attainment of the Union’s objectives.[41] The relevance of this duty of primary importance has grown steadily over time in the sphere of EU external relations. In Commission v Hungary (Reclassification of cannabis), the Grand Chamber reaffirmed: the duty of sincere cooperation extends fully to Member States’ conduct within international organisations, particularly where the Union has adopted a coordinated position.

Viewed through this prism, Article 218(9) TFEU has acquired a stronger constitutional dimension, serving as a legal bridge connecting with Article 4(3) TEU. The elements of the logical chain are thus visibly clicking together: compliance with an ‘EU common position’ decision adopted under Article 218(9) TFEU constitutes a concrete expression of the unity of the Union’s external representation, while the principle of sincere cooperation requires Member States to preserve and uphold that unity by adhering to such decisions in international fora. Misaligned Member State action would thus not satisfy the well-established requirement that Member States must act ‘jointly, under the principle of sincere cooperation […] in the interest of the [EU].’[42] Unilateral conduct is detrimental to the Union on several accounts: it undermines the effectiveness of the EU’s international action as well as the EU’s credibility and reputation on the international scale (paragraph 158). 

The CJEU framed such unilateral action departing from the common position as a structural threat to the coherence of EU external action, not just a procedural irregularity. It is a palpable attempt to constitutionalise the unity of external representation, by stressing that even one Member State publicly dissociating itself from a common EU position weakens the EU’s credibility, reduces its negotiating power vis-à-vis third states and undermines the effectiveness of EU external policies. Differently put, the duty of sincere cooperation in this context transcends the purpose and letter of Council Decision (EU) 2021/3 and protects a distinct legal interest which is the EU’s credibility and reputation on the international stage.[43] Not observing the latter is treated as a legally relevant harm and not merely a political inconvenience.

The power of the duty of sincere cooperation is distinctly noticeable in this context, as the EU Court did not treat Article 4(3) TEU merely as a supporting principle attached to another – more technical – infringement of EU law. Instead, in a similar fashion to the Commission v Germany (COTIF II) ruling,[44] the EU Court confirmed that a Member State can independently breach the duty of sincere cooperation by acting against a coordinated EU position in an international (multilateral) body. Siding with Advocate General Medina, the judges in Luxembourg also emphasised an intra-EU dimension of this duty, which precedes the requirement of unity in external representation, by dusting off old case law. Westzucker[45] underscored, already back in the early 1970s, that it is inherent not only in the very idea of the European integration process (now called ‘EU’) but also in the application of a majority voting procedure in the Council that the Member States should emphasise their interests and raise their differences within the institutional ‘framework of the mechanics of collective discussion’ created by the EU Treaties (paragraph 156). Although Advocate General Medina concluded that Hungary’s failure to do so constituted a further, stand-alone breach of Article 4(3) TEU,[46] the CJEU stopped short of endorsing that view, treating the point instead as an additional supporting consideration in finding a violation.

At the same time, the judgment in Commission v Hungary (Reclassification of cannabis) raises important questions about the balance between the unity of external representation and diversity within the EU. By imposing strict obligations on Member States to adhere to common Union positions, the EU Court somewhat limits the scope for national differentiation and dissent – although these are to be channelled and expressed in EU decision-making processes, namely in the Council and its preparatory bodies as per the Westzucker dictum. However, this may be problematic in policy areas that are politically sensitive or culturally contested, such as drug policy. Critics may argue that the EU Court’s approach prioritises coherence over pluralism and that it risks alienating those Member States whose domestic preferences diverge from the EU consensus. This raises concerns about the transformation of Article 4(3) TEU into a ‘catch-all’ principle. By invoking the duty of loyal cooperation, the EU judiciary is able to impose legal obligations in politically sensitive policy areas and circumvent the need for more detailed analysis of the limits of EU powers. 

While this enhances the effectiveness of EU action, it also creates risks for legal certainty. The boundaries of the duty enshrined in Article 4(3) TEU are inherently open-ended, making it difficult for Member States to predict the legality of their conduct in all scenarios. Added to this, this core EU structural (integrationist)[47] principle may be used to discipline political dissent, particularly where Member States disagree with the substance of EU positions rather than their legal basis under the EU Treaties.

6.   Conclusions

The Grand Chamber judgment in Commission v Hungary (Reclassification of cannabis) marks a significant step in the evolution of EU external relations law and its constitutional centralisation. Through its rather expansive interpretation of EU exclusive external competence (Article 3(2) TFEU) and the robust and self-standing application of the duty of sincere cooperation (Article 4(3) TEU), the CJEU chose to reinforce the unity of EU external action while simultaneously narrowing the scope of Member States’ unilateral margin of manoeuvre as sovereign actors in international fora. 

In practical terms, the ruling is likely to have far-reaching consequences for the conduct of Member States within international organisations, including those in which the EU is not – and cannot be – a formal member.[48] It sends a clear signal to Member States that deviations from EU-coordinated common positions will not be tolerated and may result in infringement proceedings condemning them. This may lead to greater discipline and consistency in EU external representation, but it may also discourage open debate and the expression of dissenting views within international fora. Member States may feel compelled to conform to EU positions even where they have strong reservations (e.g. in sensitive policy fields), with a view to avoiding intra-EU legal repercussions.

Summing it up, this case should be understood not merely as a technical infringement ruling – although the Grand Chamber format clearly sends a message about the gravitas of the issues dealt with therein – but as an important brick in the edifice of continuously transforming the law governing EU external relations into a more integrated (constitutional) and more mature one. As such, it is likely to become, in the field of EU external relations law, a focal point for further judicial development by the CJEU in the years to come.