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  • Writer's pictureJosh Thompson

Sovereignty and Subject: HLA Hart and the Doctrine of Supremacy

Updated: Apr 19, 2022

Supremacy delineates the relationship between the member states and the EU. EU law exists within the broader realm of international laws however EU law is differentiated from other forms of international law in that EU constitutes a sui generis legal system to which the Member States have voluntarily limited their sovereignty in some respects. There is no express reference to the term “supremacy” within the Treaties and the doctrine emerged by way of judicial activity in the Court of Justice where the Court has repeatedly reaffirmed that doctrine is implied within the Treaties. While some may find the idea of limiting a state's sovereignty in some regards alarming or a form of abstract imperialism on the part of a stronger Member State inflicted upon another weaker Member State, the concept really shouldn’t be that concerning at all. Often the responses many have toward the doctrine of supremacy stem from a lack of understanding as to the purpose of the doctrine and why it has come to occupy a constitutional position within the EU legal order.

At the heart of the concept of supremacy is the paradox of sovereignty and the binding nature of EU law. Accordingly, it should come as no surprise that the doctrine of supremacy has acted as a lightning rod for a variety of political narratives, nationalistic ideologies and even conspiracy theories of which are so numerous and detailed that they constitute an entirely separate discussion altogether. During Brexit the doctrine of supremacy adopted a center stage position under the guise of “taking back control”(1). The Brexiteer himself Nigel Farage criticized the concept of supremacy by saying “I believe we’re big enough and good enough to govern our own country.”(2) The doctrine of supremacy has become a reoccurring theme throughout the rapidly developing case law emerging from the current rule of law crisis in the EU illustrating the importance of supremacy as a necessity in reaffirming the rule of law as a concept within both the EU legal system and in national legal systems. The rule of law crisis is ongoing and important development in the rule of law crisis has manifested before the Polish Constitutional Tribunal in the form of Case K3/21 where very concept of supremacy is being challenged.(3)

It is against the context of the rule of law crisis and Case K3/21 that I wish to explore the doctrine of supremacy and the binding nature of EU law using the work of HLA Hart as a source of guidance. Hart presented his views on international law in the The Concept of Law. The publication itself represents a fundamental piece of work in the positivist tradition and one that has proven relevant some 60 years later. While Hart doesn’t go so far as to present a full thesis on international law his views on international law as a system of rules represents a problematic position in light of the development of supremacy within EU law.

Hart’s view on international law is an exploration of the paradox between sovereignty and the binding nature of international law. Through the deconstruction of Hart’s views on international law that I wish to explore the nature of supremacy and in turn provide what I believe to be a compelling argument for the relevancy of Hart's concept of law within the context of EU law.

1. Hart’s concept of law

When opening up any form of discussion regarding a principle or concept that is law-related it is always useful to first establish what is law? This line of enquiry is also applicable to understanding what is international law. In The Concept of Law, Hart applies his formulation of a legal system as being a union of primary and secondary rules to the concept of international law. Accordingly, it is essential that the basics of Hart’s thesis on law is outlined as a preliminary point before moving to consider Hart’s views on international law as his views would make little sense without the context of his broader thesis. It is my intention in this section to present Hart’s thesis of law as a social tool existing with a legal system which is a union of primary and secondary laws.

This question can be understood to have two implications; what is the definition of law and what is law as a concept? The first question is best understood as meaning a substantive view of the what is question while the second is entails a more abstract analysis. According to Hart, law possesses a social function and as such law in the abstract provides a set of guidelines which guide human behavior in all aspects of social life.(4) This version of law might differ to the version of law the general public would identify as law. If asked the what is question most member of the general public would probably emphasis the punitive aspects of a law when trying to describe law as a concept. A lawyer might approach the question form a slightly different angle and note the authoritative nature of law. The reality is both are more or less answering the question in the same way; the law is the law and it must be followed otherwise some form of punishment awaits the deviant.

These are not satisfactory answers nor are they productive approaches to take when grappling with the what is question of law. This is to do with the distinction between rules and laws. Simply possessing authoritative or punitive features cannot be enough to outline the content of law nor is it enough to firmly establish a legal order within which all laws are neatly placed in a hierarchical order. A law becomes a law once it is recognized as such; the rules of recognition. This concept of validity by recognition implies two meanings; firstly, a law is recognized as being a valid law where it is generally understood as complying with the rules of the legal system in a hierarchal context.(5) Secondly, validity also entails a social or psychological component; a law is recognized as a law not because of its punitive content but because of the hypothetical deviation of the law acting as the coercive element. Every day property is sold, contracts are signed, and we can leave our homes confident that we will not be attacked in the streets. This is possible because of the clear social guidelines provided by the law and the generally accepted understanding that deviation from the guidelines is the exception and not the norm.

Hart outlines the binding nature of law as a rational recognition of the status quo. According to Hart, individuals, of equal characteristic, living in close proximity are required to voluntarily submit to the law so that they will not become victims of malefactors.(6) In Hart’s view the natural deterrents attached to deviant behavior would never be enough to provide sufficient protection for the individual. Hart continues and concludes the same cannot be said for a state due to the costly and risky attributes associated with the closest comparative action between an individual being a victim and a state becoming a victim; war. (7) Hart rationalizes the binding nature of international law arises from the risks associated with war and the mutual needs of the states.(8) Lowe approached the binding nature of law in much the same way as Hart formulating that international law is made to suit the needs of those who draft and sign them.(9)

Recognizing a law as a binding obligation is significantly more complicated when discussing international law. Whereas with national laws we are able to identify some core elements; authoritative, punitive, etc., it is much more difficult to do the same for international law. I can recognize a specific national law as being a law with little difficulty. I can recognize the guidelines of the law provided the law is sufficiently clear, I can assume the benefit of observing the law and I can rationalize why this is so. This pattern of interaction can be defined as a primary rule.(10) Further, I can also identify the law with reference to the national legal system I live in through the material fact that there is a written constitution in my country of residence, and institutional structures that are easily identifiable. These institutions provide for the recognition, change and adjudication of laws. This contextual view can be defined as a secondary rule.(11) Hart proposes that by combining the primary and the secondary a legal system is created and social order is established.(12) This formula might be preproperate when contemplating national legal systems and laws but when applied to international law the discussion becomes more complex and there are a number of difficult issues that require addressing.

Strictly speaking, most forms of international law are treaties and most treaties lack institutional formalities such as a legislative or a court. Thus, we can say international law implies obligations or primary rules upon states but lacks secondary features. According to Hart international law is more comparable to basic social structures rather than the more advanced legal system. Hart presents his views on international law as a system of primary rules rather than a full legal system due to the lack of any observable secondary rules. At the time of writing The Concept of Law, EU law did not exist in its current form and mechanisms for the enforcement of binding obligations was restricted by the operation of a veto mechanism. Hart cites the United Nations Security Council as provided for under Chapter VII of the UN Charter as an example of such a phenomenon. Per the Charter, the binding nature of any obligations arising under the UN Charter are subject to a veto mechanism thus paralyzing any probability that such an obligation could be truly enforced.(13)

2. An analysis of Hart’s views on international law

Discussions regarding the doctrine of supremacy either academic, or in a political context usually, if not always, revolve around the concept of sovereignty. It is for this reason that Hart’s work on international law is still relevant as a guiding tool for the exploration of supremacy and the binding nature of EU law. It is obvious that Hart is incorrect to suggest international law is incapable of being defined as a legal system however as briefly noted above, this is partly due to the era in which Hart wrote The Concept of Law. It is a statement of fact to define EU law as a legal system, and as EU law is technically a form of international law this obviously raises some difficulties regarding Hart’s hesitation to ascribe the definition of a legal system to international law. Nonetheless, Hart’s views on international law are constructive to understanding the nature of supremacy as in the process of presenting his view Hart explores the paradox of sovereign and subject which directly relates to the operative necessity for the doctrine of supremacy and the need for an international legal system as opposed to a system of rules. The Concept of Law has proven its worth over time and Hart’s continues to offer guidance in the positivist legal tradition.

In The Concept of Law Hart notes the formulation of a legal system as being a union of primary and secondary rules. Hard confirms international laws possess features approximate to primary rule but that the secondary rules as absent. Hart continues and notes that of the secondary rules it is the rule of recognition which constitutes the ultimate rule and as such the most important in differentiating a system of rules from a legal system.(14) Per supremacy a rule of recognition has been bestowed upon the EU legal order and as such has transformed EU law from a system of rules into a legal system and as such EU law constitutes an international legal system.

My intention with this section is to outline Hart’s views on international law and in doing so use his critiques of the voluntary theories of international law and the theory of morality as international law as a guiding tool through which the paradox of sovereignty and subject can be explored and in turn the binding nature of supremacy explained and further understood. This exercises doubles as an example of Hart’s continuing relevancy to the positivist legal tradition and constitutes a revisiting of Hart’ views on international law in light of modern developments in international jurisprudence.

2.1: The paradox of sovereign and subject

The binding nature of EU law through supremacy exists in a state of paradox as each of the Member States exists as sovereign states and therefore it would be contradictory to say a sovereign state could be found to be fully bound by an obligation arising from international law. The paradox between sovereignty and the binding nature of international law presents the how question; how is international law binding? In The Concept of Law Hart provides his views on international law and in doing so explores the nature of sovereignty, promises and the formulation of a binding obligation. (15) While it has been settled that the supremacy is rendered possible due to the limitation of a state’s sovereignty in some respects it is not entirely settled as to how this is so. Three major schools of thought in this regard are the self-limitation theory, the consent-based theory and the moral international law theory. In his thesis, Hart dismisses each of the three mentioned theories as satisfactory answers to the how question regarding the binding nature of international law and in doing so he presents his own solution; international law is not a legal system per se but rather a set of rules.

Hart begins his thesis by observing that those who exist within a state governed by the rule of law are considered subject of the law. If a state is bound by international law this would naturally imply the state is also a subject. This statement requires an exploration of Hart’s definition of sovereignty. The concept of sovereignty is defined by Hart so at to act as an approximate conversion of independence; a sovereign state is one not bound by varying forms of control and it is sovereignty is defined by those areas of conduct within which the state is autonomous.(16) Hart’s position on sovereignty contrasts Austin’s formulation of the sovereignty authority in his command theory as according to Hart it isn’t the sovereign who makes the rules but rather the rules define the scope of the sovereign.(17)

Hart adopts the position that independence exists not as an absolute but in degrees and accordingly sovereignty should be viewed as a legal concept.(18) According to Hart a state is defined as being a fixed population and territory under the rule of an organized government which enjoys some form of independence. A legal system within a state may not accurately reflect the level of independence, or dependence enjoyed by the state. This is so because a state may exist within the context of a broader structure such as a union, a federation, a confederation and so on. Within this context a state can be understood to be independent in some aspects but dependent in others. Hart provides the example of territorial dependence citing the US and its federal states as a reference to outline how one state may be dependent upon another territory but still independent in terms of certain capacities.

An important component of Hart’s positivist theory is the concept of a legal subject. Hart observes that those who exist within a state governed by the rule of law are considered subjects of the law. Following the same logic so too are states considered subjects in some capacity; a state is subjects to their international obligations. However, such a position proves difficult when we factor the sovereignty of a state to the definition of a binding obligation and the relationship of a subject vis a vis the law. Querying whether or not a sovereign state can be truly bound by international law is an acceptable form of enquiry as Hart correctly identified that the ideals of subject and sovereignty is wholly inconsistent.

Hart continues and predicts that the contradictory nature of the voluntary theory would be acutely obvious in the event that international law will be reinforced by a system of sanctions.(19) Hart attempts to reconcile the contradiction of a state simultaneously existing as a sovereign entity and a subject to international law by stating that international law is not binding due to consent, self-limitation or morality but rather international law exists as a set of rules and not a legal system by virtue of international law possessing the primary features of law only.(20) As such, the secondary is absent, namely the rule of recognition which would entail basic institutional structures such as a court or legislature.

2.2: Hart’s critique of voluntary international law

Hart defends his view of international law as a system of rules by presenting a three-part critique of the alternative models for international law; the self-limitation theory, the consent theory and the moral theory.(21) Hart begins his defense by first dismissing the self-limitation and consent-based theories by presenting three arguments.(22) The first argument is that self-limitation theory fails to outline the manner in which an absolutely sovereign state can become bound by an obligation; how can an absolute sovereign state become bound? This argument partly refers back to the prior paradox of independence vis a vis a binding obligation outlined above. It is Hart‘s view that the concept of self-limitation is inherently incompatible with the binding nature of international law as self-limitation essentially amounts to a promise to impose an obligation. This suggests that there must exist a separate rule which stipulates that a state will carry out this obligation.

Hart observes that this form of logic is circular in nature as the concept of self-imposing obligations cannot deduce their binding nature by reference to a self-imposing obligation.(23) Hart accepts that it is possible for a binding obligation to arise from a promise however there must exist a rule providing for a binding obligation as a concept distinct from a promise.(24) According to Hart, under the self-limitation theory in order for an obligation to be binding there must exist some rule or rules providing for the binding status of the obligation. Where such a rule exists then an obligation is binding irrespective of whether or not the party chooses to be bound by it. By presenting self-limitation as an inconsistent basis through which the binding nature of an obligation is established, Hart is deconstructing the concept of absolute sovereignty and in turn endorsing his rule-based theory.

The second criticism of the voluntary theory presented by Hart is the need to distinguish the a priori claim made by supporters of the consent-based theory that a state can only be bound by self-imposed limitations from the claim that a state could potentially be bound under a different system.(25) Per Hart consent is implied or given ’tacitly’ with results in consent being no more than a fictions concept in the context of international relations.(26) Hart provides an example of this tacit consent by providing the following observation; where a state experiences a change in territory and finds its self with newly acquired access to the sea this state would find itself bound by all of the international laws applicable to territorial waters and the high seas. In such a case this state would find itself subjected to rules to which it had never observed and as such the state was never in a position to exercise any form of consent regarding those rules. The primary objective of Hart in this portion of his critique is to establish there are instances wherein a state may find itself subjected to rules without having the opportunity to provide or even contemplate any notion of consent.

2.3: Hart’s critique of morality as international law

Hart maintains his positivist approach to law in his views on international law. Hart dismisses the use of moral based rules as a mechanism through which relations between states can be regulated.(27) Hart cites the indifference of law to morality. This relates to Hart’s proposal that law fulfills a social function and serves as a source of guidance through which social conduct can be regulated. In his municipal theory of law Hart dismisses the presumption that morality is necessary to law and in doing so critiques the position that a moral obligation arises between the legal subject and the law.(28) The key to untangling morality from law lies in the principles of justice.(29) Hart frames the concepts of just and unjust with fair and unfair. Hart decouples justice from morality by establishing the concept of justice as equality. Within this position equality plays a central role in conveying the Hartian definition of justice.(30) According to Hart the correct approach to justice is not to rely upon morality but to” treat like cases alike and different cases differently”.(31) In short, Hart’s view on justice as a conversion of morality within the context of positivist theory equates not to individual conduct but the ways in which classes of individuals are treated.(32)

Turning to international law Hart imports his theory on moral obligation on a municipal level to the international level.(33) Moral obligation implies a form of social pressure to ensure law is binding and as such moral rules are supported by moral pressure.(34) Moral pressure is applied within the context of a social structure and per Hart states lack such social structures and thus are not susceptible to moral pressure.(35) Hart continues and outlines that content of binding obligations often lack moral content as the purpose of such laws is to provide guidance irrespective of moral implications or considerations.(36) Hart rejected the need for deeper foundational principles when defining a legal system. Morality was not necessary to explain why a rule is recognized. Hart adopts a constructive social view and states that binding rules exist because the society thinks of them as such.(37) For Hart morality is an unnecessary concept and his position regarding the relevancy of morality within a municipal legal system is echoed in his views on international law.

2.4: EU Law as an international legal system: legality and the EU legal system

It is here, at this juncture, amongst the paradox of sovereignty and subject that we return to the primary focus of this article; the doctrine of supremacy. The doctrine of supremacy poses difficulties when viewed vis a vis sovereignty and even attempting to rely upon Hart’s formulation of international law as a system of rules is not enough to settle the paradox of sovereignty and subject. It is clear that Hart did not wish to define international law as a legal system due to the lack of any noticeable secondary rules. As such according to Hart international law is better understood as a primary system of rules comparable to a basic form of societal structure within a state. Hart’s view largely stem from personal experience and the era within which he lived. Supremacy represents a radical development in international legal theory and through supremacy a body of international law was constituted formally that possess both primary and secondary rules. EU law constitutes a body of international law that possess a full legal system and enjoys a compulsory jurisdiction and institutional structures satisfying Hart’s formulation of a legal system as a union of primary and secondary rules.

I do not believe the existence of EU law as a form of international legal system highlights a flaw in Hart’s approach to international law nor does it undermine the value of Hart’s positivist theory. Hart suggested that for international law to be considered a legal system the existence of secondary rules would be required.(38) In addition, Hart references the lack of a legislative change mechanism as a defect that may require repairing at some point in the future.(39) Supremacy marks a shift within the EU structure from a set of rules to a full legal system and in the process a number of institutional features were required to ensure such a system could form and function. The features I am referring to are the development of a legislative authority to enact change and the binding jurisdiction of the CJEU providing for the recognition of rules and the adjudication of conflicts.

Per Hart, such institutions can be understood to represent secondary rules as they allow for the recognition of laws, the changing and adjudication of laws and lastly the persistence of laws within the legal order. It is for this reason that Hart’s formulation of law proves relevant within the context of EU law and the concept of supremacy acts as an important operative mechanism for the EU legal order. As it is a legal system such a system requires legality which is achieved through supremacy.(40) Legality is foundational to the operation of any legal order and instrumental to the rule of law. To better understand the relevance of supremacy to the rule of law it is important that the genesis of supremacy as a doctrine is briefly considered.

Despite representing a constitutional principle within EU law supremacy is not referenced explicitly within the Treaties but since the foundational decision of the ECJ in Van Gend en Loose, the ECJ has repeatedly reaffirmed that the doctrine of supremacy as one implied in the Treaty framework.(41) Article 4 TEU outlines a positive obligation upon both the Member States and the Institutions of the EU to take all measures to ensure the fulfillment of the Treaty objectives and to avoid taking any action that would otherwise impede the fulfillment of these goals. Supremacy can be viewed as a recognition of necessity; to ensure the vindication and protection of a treaty obligation EU law must possess legality or supremacy and thus it must supersede national law.(42) In Simmenthal the ECJ confirmed that EU law must be applied in full and in the event of a conflict between EU law and national law it is the national measure that must be set aside.(43) In Costa v ENEL the ECJ outlined the limiting nature of supremacy and that by adopting the Treaties, the Member States agreed to limit their sovereignty in certain regards.(44) Such a limitation arises from the Treaties implicitly and as a necessary requirement for the fulfillment of the obligations contained within the Treaties. The formulation of supremacy as confined limitations on competencies closely resembles Hart's formulation of sovereignty outlined prior.

Hart’s reservations regarding the use of the term legal system in relation to international law. The Concept of Law was initially published in 1961, just two years before the genesis of supremacy in the 1963 decision in Van Gend en Loos. The accuracy of Hart’s prediction is notable, and it is the relationship between binding obligations and sovereignty that has occupied center position in subsequent discussions regarding the supremacy of EU law. (45) In Costa v ENEL the ECJ outlined the limiting nature of supremacy and that by adopting the Treaties, the Member States agreed to limit their sovereignty in certain regards.(46) Such a limitation arises from the Treaties implicitly and as a necessary requirement for the fulfillment of the obligations contained within the Treaties however how such an obligation arose none the less requires consideration as the existence of such a system established rather bluntly that Hart’s hesitation to define international law as a legal system is outdated and requires revisiting. It is in light of the above reference to Cota v ENEL and need for necessity that I will present the justification for the continual operation of supremacy and why it is essential in ensuring the functionality of the EU legal system and the rule of law.

Hart’s work has proven to be influential in the positivist legal tradition yet his work in relation to international law is somewhat limited. This is largely due to his reluctance to present a full thesis on international law and instead he opted to transpose his thesis on the concept of law into an international context. Despite this Hart’s views on international law are not without merit and has such it is still relevant even in the context of an international legal system such as EU law. As EU law can be considered a legal system per Hart’s formulation of the union between primary and secondary rules this provides an explanation as to the binding nature of supremacy. In line with the Hartian view on the concept of law EU law can be viewed of as a system of guiding rules which are imposed on its members and in turn also possess secondary rules whereby conflict between rules can be settled and a mechanism for changing rules is present. The ECJ possesses full jurisdiction to adjudicate conflicts between national laws and EU law and serves as an example of EU law possessing a secondary rule.

3. Conclusion

In conclusion it is difficult to avoid a discussion regarding the paradox of sovereignty and subject when engaging in any form of dialogue relating to the doctrine of supremacy. Nonetheless, acceptance is essential for the functioning of the EU legal order and to compromise on the principle of supremacy would be a compromise on the ability of the EU and the Member States to achieve the treaty objectives and to ensure the fundamental values are applied and protected.(47) Hart’s hesitation to refer to international law as a legal system is understandable given the dominant international legal orders in operation during the time Hart first published The Concept of Law. Supremacy constitutes a remarkable shift in theory and through supremacy an international legal system was reaffirmed. Despite modern developments Hart’s work still constitutes a relevant authority in the positivist approach and as such it is still relevant to understanding the binding nature of EU law.

In his exploration of international law Hart explores the paradox of sovereign and subject and denounces a number of possible theories associated with the binding nature of international law. As EU law is a legal system it is essential that the secondary rules continue to apply and operate. Supremacy provides EU law with sufficient legality and ensures the rule of law remains a core component within the EU legally system. It is through supremacy that conflicts of national and EU law are remedied through the binding jurisdiction of the ECJ. Without EU law possessing a binding quality the objectives and values enshrined within the Treaty framework would be eroded and impossible to realize. It is for this reason that any discussion regarding the necessity of supremacy should be viewed with caution as this is not just a discussion of legality in a vacuum but a broader discussion regarding the foundation of the European Union and democracy in Europe. To restrict supremacy is to restrict the concepts of justice, democracy, equality and the rule of law. To reference Hurd;” National states are incompetent. Not one of them...can adequately provide for the needs that its citizens articulate.”(48) It is for this reason that we must continue to cooperate and to respect the legality of the EU legal system. Per Hart, sovereignty exists not as an absolute but in degrees and the concept of supremacy should not be viewed as a recent phenomenon. Sovereignty should not be conflated with independence and reduced to a simple absolute principle. Sovereignty exists in degrees and the doctrine of supremacy is fundamental to the achieving of an international legal system.



  2. See Farage, Nigel Farage: Vote leave to take back control of our destiny”, available at

  3. Pending Case K 3/21, Assessment of compliance with the Constitution of the Republic of Poland of selected provisions of the Treaty on European Union, available at

  4. HLA Hart, The Concept of Law, (1961) 3rd edition

  5. ibid, pg 104

  6. ibid, pg 218 - 219

  7. ibid

  8. ibid, pg 220

  9. Vaughan Lowe, International Law, pg 19

  10. HLA Hart, The Concept of Law (1961) 3rd edition, pg 81

  11. ibid, pg 93 - 96

  12. ibid, pg 214

  13. ibid, pg 217

  14. ibid, pg 107-110

  15. ibid, pg 217 - 223

  16. ibid, pg 223

  17. ibid, pg 222 - 224

  18. ibid, 222

  19. ibid, pg 220

  20. ibid, pg 227, 233 - 236

  21. ibid, pg 224

  22. ibid

  23. ibid, pg 225

  24. ibid

  25. ibid

  26. ibid, pg 226

  27. ibid, pg 227

  28. ibid, pg 156 - 157

  29. ibid

  30. ibid, pg 158

  31. ibid, pg 164

  32. ibid, 167

  33. ibid, pg 227

  34. ibid, pg 228

  35. ibid

  36. ibid, pg 229

  37. ibid, pg 231

  38. ibid, pg 236

  39. ibid, pg 230

  40. European Commission for Democracy Through Law (Venice Commission) Report on the Rule of Law (2011) CLD-AD(2011)003rev at pg 10

  41. C-26/62 Van Gend en Loos v Nederlandse Administratie der Belastingen

  42. C-6/64, Costa v ENEL

  43. C-106/77 Amministrazionedelle Finanzedello Stato v Simmenthal

  44. C-6/64, Costa v ENEL, pg 593 accessible at

  45. HLA Hart, The Concept of Law (1961) 3rd edition, pg 226

  46. C-6/64, Costa v ENEL, pg 593 accessible at

  47. ibid, pg 594

  48. Hurd, The Search for Peace (1997), pg 6

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