The Many Facets of the Autonomy of EU Law: Inside and Outside Views. Introduction to the Special Section

Table of Contents: 1. Setting the scene: EU autonomy and its expanding external dimension – 2. Inside and outside perspectives on EU autonomy – 3. Bridging perspectives: introducing the Special Section – 4. Concluding thoughts.

Abstract: The autonomy of EU law is a foundational principle of the European integration project. In its external dimension, autonomy shapes how the EU legal order positions itself vis-à-vis and interacts with international law. As the EU has evolved into an increasingly active international actor, interactions between EU law and international law have multiplied, and questions concerning EU autonomy arise with growing frequency. Yet scholarly debates about EU autonomy often remain divided along disciplinary lines. EU lawyers tend to analyse autonomy as a constitutional safeguard internal to the EU legal order, whereas international lawyers frequently approach it as a claim to exceptionalism within international law. As a result, these scholarly debates often evolve in parallel rather than in dialogue, limiting our understanding of the principle and how it operates at the intersection of EU law and international law. This Special Section responds to this gap by bringing together contributions engaging both ‘inside’ (EU law) and ‘outside’ (international law) perspectives and placing them in dialogue. Taken together, the contributions illustrate how the autonomy of EU law is continuously shaped both internally, primarily by the Court of Justice of the EU, and externally, through the EU’s engagement with international legal regimes. Since this is an ongoing process, the meaning of autonomy will continue to evolve as new actors, challenges, crises and technologies reshape the legal landscape. The key question for future scholarship is therefore not whether EU law is autonomous, but how that autonomy is articulated, justified, applied, and adapted in changing legal and political circumstances.

Keywords: autonomy of EU law – external dimension of autonomy – interactions between EU law and international law – EU exceptionalism – EU as an international actor – EU external relations.

1.   Setting the scene: EU autonomy and its expanding external dimension

The ‘autonomy of EU law’ is widely regarded as one of the foundational principles of the European integration project.[1] Since its judge-made creation in the 1960s,[2] ‘EU autonomy’ has played a central role in defining the distinctive character of the EU legal order as a ‘new legal order’.[3] The principle not only structures the relationship between EU law and the domestic legal orders of the Member States (internal autonomy), but also shapes the Union’s position vis-à-vis wider international law (external autonomy).[4] Given this role, it is unsurprising that the autonomy of EU law has generated a rich body of scholarship seeking to illuminate its meaning, functions, and implications.[5]

Initially, both the case law of the – now – Court of Justice of the European Union (CJEU) and scholarly attention focused primarily on the internal dimension of EU autonomy. In this context, ‘autonomy’ has been understood as safeguarding the constitutional integrity of the EU legal order: ensuring the primacy and effectiveness of EU law, preserving the CJEU’s central role in maintaining the uniform interpretation of EU law, and protecting the coherence of the Union’s system of multi-level judicial protection.[6] Yet, over time, the external dimension of autonomy – determining the way in which the EU legal order positions itself vis-à-vis and interacts with international law –[7] increasingly gained both practical significance and prominence in scholarly debates.[8] As the EU has progressively developed into a fully-fledged international actor, its engagement with international law has intensified across a wide range of substantive fields, including trade, investment, migration, environmental protection, and human rights. This growing internationalisation of EU action has generated increasingly complex forms of legal interactions between EU law and international law.[9] On the one hand, the EU actively seeks to shape the development of international norms in areas where it exercises regulatory authority.[10] On the other hand, international law simultaneously penetrates and influences the EU legal order.[11]

In this evolving landscape, EU autonomy has come to operate as a key organising principle governing the relationship between the EU legal order and wider international law. Consequently, autonomy has become a subject of growing interest not only for EU lawyers but also for international lawyers.[12] Yet, despite this shared interest, EU lawyers and international lawyers, perhaps unsurprisingly, have often approached the issue from within their respective disciplinary frameworks. As a result, discussions of the autonomy of EU law frequently develop in isolation.[13] The price of this disciplinary separation is that our understanding of how ‘autonomy’ operates at the intersection of EU law and international law remains incomplete.

2.   Inside and outside perspectives on EU autonomy

The distinct approaches to studying EU autonomy and the operation of its external dimension reflect both disciplinary divides and deeper differences in how the notion is conceptualised from ‘inside’ and ‘outside’ the EU legal order.

From an inside, EU law perspective, autonomy is closely linked to the EU’s constitutional architecture. It expresses the idea that the EU legal order possesses essential characteristics that distinguish it from ‘ordinary’ international law.[14] In the jurisprudence of the CJEU, autonomy functions as a structural safeguard ensuring that external commitments do not undermine the fundamental principles governing the EU legal order.[15] In this sense, autonomy serves to protect the internal coherence, effectiveness, and institutional structure of EU law – and ultimately the values on which the EU is founded.[16]

From an outside, international law perspective, the very premise that the EU’s characteristics warrant a ‘unique’ position of the EU legal order within international law is subject to debate.[17] Rather than emphasising the EU’s constitutional singularity, international lawyers and external actors tend to focus on the limits that international law places on the Union’s claims to an exceptional status.[18] From this viewpoint, autonomy may appear less as a constitutional necessity and more as a boundary-drawing device that shapes the EU’s participation in international agreements, dispute-settlement mechanisms, and global governance structures.[19]

These different perspectives increasingly intersect in practice. As the EU deepens its engagement with international legal regimes, questions regarding the autonomy of EU law arise in ever more diverse contexts. International courts and tribunals, international organisations, and third states are frequently confronted with the EU’s claims regarding the special nature of its legal order.[20] In some instances, these claims are accommodated; in others, they generate friction and legal uncertainty.[21]

This growing interaction has exposed a structural challenge in the scholarly debate. As EU lawyers and international lawyers often approach the issue from different analytical starting points or angles, discussions about EU autonomy sometimes proceed in parallel but isolated spheres rather than in dialogue. Yet, precisely at the intersection between EU law and international law – where the principle of EU autonomy performs some of its most consequential functions – a more integrated perspective is needed.

Understanding the autonomy of EU law, therefore, requires moving beyond disciplinary silos. Only by bringing together insights from both EU law and international law can scholars fully capture the relational character of autonomy: a principle that simultaneously safeguards the integrity of the EU legal order and structures its engagement with wider international law.

3.   Bridging perspectives: introducing the Special Section

Responding to this challenge, the present Special Section brings together established and emerging scholars working in both EU law and international law to examine the autonomy of EU law from diverse but complementary vantage points. Engaging both ‘inside’ and ‘outside’ perspectives and bringing them into dialogue, the contributions shed new light on the principle of autonomy and its operation in the increasingly dense and multifaceted interactions between EU law and international law. In doing so, they contribute to a fuller and more integrated understanding of the autonomy of EU law – one that recognises the principle as both shaping and being shaped through the Union’s interactions with wider international law.

The contributions included in this Special Section were first presented at the international conference titled ‘The Autonomy of EU Law Under Pressure? The Changing Landscape of the Interactions Between EU Law and International Law’,[22] convened by these guest editors at WU Vienna University of Economics and Business in January 2025. Following the event, selected papers were further developed and refined through several rounds of internal and external peer review. The resulting contributions – published in two batches – approach the autonomy of EU law from a range of conceptual, institutional, and sectoral perspectives, illustrating how it is interpreted, contested, and reshaped at the intersection of EU law and international law.

A first group of contributions revisits the conceptual and doctrinal foundations of the autonomy of EU law, primarily from an ‘inside’ EU law perspective while situating these developments within broader debates in international law. Stefan Mayr examines the evolving contours of the CJEU’s external autonomy doctrine by identifying two conceptual dynamics – ‘snowballing’ and ‘yoyoing’ – that characterise the Court’s case law on that matter and contribute to the continuing elusiveness of the autonomy principle. Through an analysis of the Court’s investment arbitration-related case law and the debate surrounding the EU’s accession to the European Convention on Human Rights (ECHR), the article illustrates how the Court’s shifting levels of scrutiny shape the EU’s engagement with external dispute-settlement mechanisms, but also make this engagement quite unpredictable. Cristina Contartese similarly revisits one of the earliest judicial articulations of EU autonomy in Commission v Luxembourg and Belgium (1964) but does so by placing the Court’s judgment within the international legal debates of the time. By examining the notion of ‘legal order’ from an international law perspective, the article challenges the idea that the autonomy of EU law represents a wholly exceptional feature of the Union’s legal architecture and instead situates the Court’s reasoning within broader conceptual developments in international law.

A second group of contributions examines the institutional tensions that arise when the EU’s internal understanding of autonomy encounters external legal regimes and international adjudicatory bodies. Sarah Thin and Nariné Ghazaryan approach the issue from a perspective grounded in international law, scrutinising the CJEU’s claim to exclusive jurisdiction vis-à-vis international courts and tribunals. By juxtaposing the Court’s jurisprudence with international legal principles governing adjudicative jurisdiction, the article questions whether the external dimension of EU autonomy ultimately rests on recognition by external actors. Péter Budai explores similar tensions in the context of the EU’s long-standing project of accession to the ECHR, analysing recent developments in the Court’s case law concerning the scope of judicial review in Common Foreign and Security Policy (CFSP) matters. Through the lens of different dimensions of autonomy identified in academic literature, the article assesses whether these case law developments bring the EU closer to resolving the autonomy concerns that complicated the EU accession process. Complementing this institutional perspective, Ágoston Mohay examines how the autonomy of the EU legal order shapes the evolving architecture of judicial protection within the Union. By analysing developments concerning remedies in CFSP matters, the possible implications of the EU’s accession to the ECHR, and the extension of standing to third states before the CJEU, the article illustrates how the principle of autonomy operates simultaneously as an internal constitutional safeguard and as a factor structuring the EU’s engagement with external systems of judicial review.

The final group of contributions explores how the interaction between EU autonomy and international law unfolds in specific substantive policy areas where the two legal orders are deeply intertwined. Julie Farrah Yassine scrutinises the relationship between EU autonomy and international human rights law from an explicitly international law perspective, arguing from this ‘outside’ viewpoint that an overly rigid conception of autonomy risks generating fragmentation and undermining the EU’s external legitimacy as a global human rights actor. The article advocates for a more pluralist and cooperative understanding of EU autonomy grounded in mechanisms such as judicial dialogue and consistent interpretation. Valeria-Anna Kokkinou and Kalypso-Sofia Sdrali address similar tensions in the field of asylum and migration law by analysing how EU law navigates the relationship between EU autonomy and the customary international law principle of non-refoulement. The contribution also highlights the difficulties in reconciling the EU’s constitutional structure with questions of international responsibility and accountability in the context of migration governance. Ioanna Hadjiyianni, in turn, unpacks the interactions between EU autonomy and international environmental law through the example of access to justice under the Aarhus Convention. The article demonstrates how international environmental compliance mechanisms have acted as a catalyst for reform within the EU legal order while also exposing the delicate balance between preserving institutional autonomy and ensuring meaningful compliance with international environmental obligations. Finally, Andrej Lang examines the EU’s emerging doctrine of ‘open strategic autonomy’ in external economic relations through the example of the EU’s Anti-Coercion Instrument. By analysing the instrument’s compatibility with both EU primary law and WTO obligations, the article illustrates how the EU seeks to reconcile a more assertive conception of its autonomy with its longstanding commitment to a rules-based international economic order.

Taken together, these thoughtful contributions illustrate how the autonomy of EU law is continuously shaped both internally, primarily by the Court of Justice, and externally, through the EU’s engagement with international legal regimes. By examining both doctrinal and jurisprudential developments within the EU legal order and the responses of external actors and (judicial) institutions, the articles highlight the relational and evolving character of the principle of autonomy in contemporary EU law.

4.   Concluding thoughts

As the contributions in this Special Section demonstrate, the autonomy of EU law is neither a static nor monolithic concept. It is a multifaceted and constantly evolving EU legal doctrine of constitutional importance. If the past decades have been devoted to solidifying EU autonomy as a principle of self-preservation, the coming decades will test its adaptability. The EU now operates in a world marked by geopolitical volatility, technological acceleration, and intensifying interdependence. Regulatory power increasingly transcends territorial boundaries; digital infrastructures defy traditional jurisdictional lines; climate governance, public health, migration, multilateral trade, investment protection, and security demand novel forms of cooperation that strain classical constitutional categories. In this environment, the principle of autonomy cannot remain a defensive posture – it must become a constructive framework for engagement.

The contributions in this Special Section collectively suggest that EU autonomy is best conceived as relational. It is shaped through dialogue, refined through contestation, and sustained by mutual recognition among overlapping legal communities. EU autonomy does not silence legal pluralism: it structures it. It provides a vocabulary, from the EU’s point of view, for managing the inevitable tensions that arise in multi-layered legal landscapes.

In this sense, EU autonomy is not the endpoint of the European integration project through law but an ongoing project. It reflects the Union’s effort to reconcile authority and openness, internal legal unity and strict observance of international law, as well as constitutional identity and global responsibility for multilateralism. Its meaning will continue to evolve as new actors, challenges, crises and technologies reshape the legal landscape. The future of EU autonomy thus lies in calibration. After all, the decisive question is not whether EU law is autonomous, but how that autonomy as a dynamic concept is articulated, justified, applied, and adapted in changing circumstances – both internally vis-à-vis Member States’ national legal systems; and externally, in the Union’s legal interactions with the wider world.

In the guest editors’ views, this Special Section, by offering both ‘inside’ and ‘outside’ views, will bring us closer to finding answers to these pressing questions by shedding light on underexplored phenomena and putting some classics into new refractions – illuminating how the EU legal order defines, defends, and reimagines itself in an evolving global (legal) landscape.