A number of publications highlight different aspects of that relationship.

(a) They try to explain the reasons for the perceived increased engagement of domestic courts with international law, which is in part due to the changing nature of international legal norms from traditionally 'outward-looking' (state-to-state) to 'inward-looking' (obligating the state to take certain action within the domestic legal order.

(b) They map out the ways in which international law is 'domesticated', ie introduced into domestic legal orders, and, more importantly, the ways in which domestic courts engage with international law in the sense of different 'strategies' or 'postures' they adopt (avoidance, alignment, contestation).

(c) They discuss the dual role of domestic courts as both law-makers and law-enforcers in international law, making it difficult to determine whether they are actually a source of law, or a method of enforcement of the law, or indeed both, much like light may be both a wave and a particle.

(d) They focus on related issues, such as the influence of domestic courts' jurisprudence in the formation or interpretation of international law. 


Antonios's work on these issues has culminated in a lecture for the United Nations Audiovisual Library of International Law.

His work was also instrumental in the creation of a Study Group ('Principles on the Engagement of Domestic Courts with International Law) within the International Law Association which worked between 2011 and 2016 and presented its Final Report to the Association at the Johannesburg Conference in 2016. The Final Report is available to download from the ILA website as is the Resolution of the Association .


Antonios was invited to teach a Special Course on the subject in the summer session of the Xiamen Academy of International Law in 2017. 



  • A Tzanakopoulos, 'Domestic Courts in International Law: the International Judicial Function of National Courts' (2011) 34 Loyola of Los Angeles International & Comparative Law Review 133
    As the title suggests, this paper does not deal with 'international law in domestic courts' but rather with 'domestic courts in international law'. It seeks to ascertain whether domestic courts are assigned an international judicial function by international law, and whether and to what extent they are in fact assuming and exercising that function. The paper attempts to define the concept of an ‘international judicial function’ and argues that, because of the peculiar ‘directionality’ of a great many international obligations (which require implementation within the domestic jurisdiction), domestic courts are the first port of call and the last line of defense for the interpretation and application of international law. However, as organs of States, courts may engage the international responsibility of the State if their conduct results in the breach of an international obligation. This is why the exercise of the international judicial function of domestic courts is supervised by States, either through the submission of disputes to international courts, or, more usually, through decentralized reactions.
    ISBN: 1533-5860
  • A Tzanakopoulos, 'Judicial Dialogue as a Means of Interpretation' in HP Aust and G Nolte (eds), The Interpretation of International Law by Domestic Courts: Uniformity, Diversity, Convergence (Oxford University Press 2016)
    This chapter discusses whether judicial dialogue on international law between domestic courts may be conceptualised as a new means of interpretation--beyond the Vienna Convention on the Law of Treaties. After defining 'dialogue' and presenting its various potential iterations, the chapter argues that in fact judicial dialogue between domestic courts is required under international law, including the Vienna Convention. This is because domestic court decisions on international law may constitute subsequent practice which is to be taken into consideration when interpreting a treaty, in accordance with Article 31(3)(b) VCLT. But domestic court decisions may also constitute practice and/or reflect opinio juris, which domestic courts must find in order to determine the existence and content of customary international law. As such, domestic courts must engage with the relevant decisions on international law by domestic courts in other jurisdictions. They must engage in judicial dialogue as a means for interpreting international law.
  • A Tzanakopoulos, 'Domestic Courts as the “Natural Judge” of International Law: A Change in Physiognomy' in JR Crawford, S Nouwen (ed), Select Proceedings of the European Society of International Law (Hart Publishing 2012)
    This paper examines whether domestic courts can be cast as the ‘natural judges’ of international law. ‘Natural judge’ is meant here in the sense of the ‘immediate,’ ‘ordinary’ judge of international law, who can only be removed through a centrally instituted judge. Given the lack of a centrally organized international judicial system, the suggestion that domestic courts are the ‘ordinary judges’ of international law has significant repercussions on the physiognomy of the international legal system. Despite the fact that in some of the decisions the reasoning of the courts is based solely on domestic law, the domestic law relied on - typically fundamental rights - is of universal radiance, as evidenced by almost universally ratified treaties and customary international law. Domestic courts are then in fact applying law based on internationally agreed standards as the immediate judges, offering effective remedies for the violation of rights influenced or shaped by, or interpreted under, international law. This trend can signify the move to a more effective application of international law, one taking place in court, even if a domestic court, rather than by a decision of the executive to invoke responsibility of another actor, or bring an international claim.
    ISBN: 9781849462020
  • A Tzanakopoulos, 'Judicial Dialogue in Multi-level Governance: the Impact of the Solange Argument' in OK Fauchald, A Nollkaemper (ed), The Practice of International and National Courts and the (De-) Fragmentation of International Law (Hart Publishing 2012)
    States increasingly 'contract out' their governmental authority in favour of international organizations. As a result, remedies available under domestic law to individuals and legal entities may no longer be available, leaving them without redress. (Domestic) courts have devised a method to react to such diminution of their jurisdiction, which at the same time comprises a message for various addressees and engages a dialogue on multiple levels. This method is shaped by the spirit and thrust of the argument the German Constitutional Court put forward in its Solange jurisprudence, and has the potential of fostering a harmonization of domestic and international law, as well as that of establishing a rudimentary normative hierarchy at the international level.
    ISBN: 9781849462471
  • A Tzanakopoulos, 'Domestic Judicial Lawmaking' in CM Brölmann and Y Radi (eds), Research Handbook on the Theory and Practice of International Lawmaking (Edward Elgar 2016)
    This contribution to the Research Handbook on the Theory and Practice of International Law-Making discusses the law-making potential of domestic courts. Given the seemingly strict 'dualist' approach of international law to domestic law and domestic court decisions ('merely facts'), the paper demonstrates the modest international law-developing function of domestic courts: it first details their methods in engaging international law, and then discusses the impact of such engagement. It concludes that domestic courts may, in terms of content, fine-tune rules of international law rather than set grand principles. In terms of process, this is done by 'suggesting' the fine-tuning, rather than in any way single-handedly developing international law.
  • A Tzanakopoulos, 'The Influence of English Courts on the Development of International Law' in R McCorquodale and J-P Gauci (eds), Contemporary Perspectives on British Influences on International Law (Martinus Nijhoff Publishers 2016)
    This contribution does not aim to quantify the influence of English courts on the development of international law, but rather to highlight their contribution in that development by focusing on important decisions on the law of immunity and on UN Law and the law of international organisations, and by referring to further notable decisions in other areas of international law. This is done against the background of an understanding of domestic courts as 'agents' of international law development through instigation, reaction, and approval, which is also explained in the paper.
  • E Methymaki and A Tzanakopoulos, 'Another Brick in the Wall -- Reflexivity of the Sources and the Enforcement of International Law: Domestic Courts as Sources and Enforcers' in S Besson and J d'Aspremont (eds), The Oxford Handbook on the Sources of International Law (Oxford University Press 2017)
    What is the role of domestic courts in the ideal continuum commencing from sources (where the law begins its life) and ultimately ending at the enforcement of the law in a specific case? Where, if anywhere, do they fit in this continuum? Put differently, are domestic court decisions a cause (source) or an effect (enforcement) of international law? What we argue in this essay is that enforcement of international law is reflexive, rather than reactive. Reflexitvity is defined as a circular relationship between cause and effect, and there is indeed such a circular relationship—a ‘feedback loop’—between the sources of international law and its enforcement: neither of the two can be finally identified as the ultimate cause or the ultimate effect. There is thus no real continuum, with domestic courts occupying this or that position on it. Rather, domestic court decisions are both part of the cause (sources) and of the effect (enforcement) of international law. The enforcement of a rule of law in a specific case constitutes, in accordance with the sources doctrine, yet another brick in the wall of that same ever-changing rule. And given the increasingly important position that domestic courts are assuming in the enforcement of international law, they become ever more important agents of development of that law, reinforcing their position in the doctrine of sources.
    ISBN: 9780198745365