1. INTRODUCTION

Over the past seven decades, the legal system of the European Union (EU) has transformed from a simple instrument of legal and economic regulation into a highly developed supranational mechanism with a wide range of political, social and security functions. In view of this, the relevance of the study is driven by the need for a deeper theoretical understanding of the mechanisms of the Union's institutional transformation in the context of growing external challenges and internal dynamics. These trends make it important to study the patterns and trends in the development of the EU legal system, to identify its key characteristics and prospects in the context of enlargement, digitalization, global instability and the restoration of the region's political role.

The purpose of this research article is to provide a comprehensive study of the evolution of the EU legal system, which combines elements of supranational, integration and political law. The article aims at identifying the key stages of transformation, determining the institutional factors of legal integration, and judicial precedents which shaped the autonomy of EU law; and also at outlining the current directions of its further development in the context of digitalization, security challenges and enlargement of the Union. To achieve this goal, an interdisciplinary approach was applied, combining a stage-by-stage analysis of the treaty architecture, institutional reforms, and case law.

Since the article addresses a political and legal phenomenon, the evolution of EU law is considered not only as a sequence of treaty amendments, but also as a process of political institutionalization. From this perspective, each legal reform simultaneously redistributed authority among the Member States, the Commission, the Council, the Parliament and the Court of Justice, and therefore changed the political meaning of sovereignty inside the Union. This approach is especially important for the modern stage, where defence, energy autonomy, enlargement and digital regulation have turned EU law into a direct instrument of strategic governance rather than only a mechanism of market integration.

2. LITERATURE REVIEW

The evolution of the legal system of the European Union is a complex multidimensional process which has been taking place over several decades in the context of deepening integration, institutionalization of supranational structures and establishment of a single regulatory paradigm. Leading domestic and foreign researchers emphasize that the EU legal system was formed at the intersection of international and domestic law, gradually acquiring features of autonomy and systematicity that separate it from both classical models of national law and the traditional international legal order.

According to Onishchenko (2010), regulation plays a key role in the structure of EU law and occupies the highest level in the hierarchy of Union legal acts, which gives it a functional analogy to a law in national legislation. This approach demonstrates the institutional maturity and internal consistency of the EU legal superstructure, which is manifested both in formal normativity and in the ability to ensure interaction with national legal systems without destroying their identity, but harmonizing their development.

Expanding the functional understanding of EU law is also highlighted by Oliinyk (2007), who views it as a special, independent system of legal relations united within unique legal architectonics. The determining factor of this system is its structural nature, i.e., a set of interdependent elements, including legislation, institutions, law enforcement practice and legal ideology, which form a single legal mechanism of an integrative nature (Оliinyk, 2007).

Instead, Yukhymiuk (2016) emphasizes the evolutionary nature of EU law principles by analyzing a set of decisions and treaties concluded within the EU. The principles that used to have declarative status have been enshrined in law and have become an instrument of judicial practice, in particular due to the active work of the EU Court of Justice, which has actually acted as a lawmaking body in the absence of case law as an official model.

The institutional and functional uniqueness of EU law is studied by D. Sukhanova, who points out that it is its ability to directly influence the legal status of individuals (i.e., EU citizens) and to form supranational mechanisms for the protection of rights and freedoms that distinguishes this system from others. The EU legal system is becoming not only a regulatory framework for states but also creates a space of legal subjectivity for individuals and legal entities, thus approaching the domestic legal order, while maintaining institutional autonomy (Sukhanova, 2024).

In scientific discourse, the EU is often positioned as a unique supranational entity whose legal system has developed through the accumulation and unification of the acquis communautaire, a set of legal acts that constitute the legal foundation of the Union (Fjelstul, 2019). However, the formation of this foundation was not linear.

The legal framework of the European Union originated from the European Economic Community, which was founded through the Treaty of Rome in 1957. Initially focused on fostering economic cooperation, the EEC gradually transformed into a broader political and legal entity, formally established as the European Union by the Maastricht Treaty in 1992 (Homewood & Smith, 2022). A major milestone in institutional reform was the Lisbon Treaty of 2007, which enhanced the EU’s governance by expanding the roles and competencies of the European Council, the European Parliament, and the Court of Justice (Kiryk, 2021). These reforms significantly improved legal enforcement and contributed to maintaining the EU’s political and legal cohesion. The continued evolution of its institutions has become increasingly vital due to the Union’s enlargement, the rising influence of intergovernmental mechanisms, and the advancement of supranational governance.

A key element in the development of the European Union was the establishment of the rule of law as a fundamental principle. As noted by Pech (2021), this concept has evolved into a central legal standard used to ensure that member states adhere to EU regulations. The Court of Justice of the European Union has been instrumental in shaping the doctrines of direct effect and the primacy of EU law, which form the foundation of the Union’s supranational legal system (Sehnálek, 2024). Recent academic work (Bast & von Bogdandy, 2024; Spieker, 2025) emphasizes the ongoing constitutionalization of EU law, characterized by a shift toward a constitutional perspective in legal interpretation and a stronger emphasis on general legal principles and fundamental rights. Nevertheless, concerns have been raised regarding the so-called “over-constitutionalization”, which some argue threatens the equilibrium between the EU’s legal independence and the national sovereignty of its member countries (Garben, 2024). The development of human rights in the EU system demonstrates a special trajectory - from initial neglect to the modern doctrine of protection that integrates the practices of the European Court of Human Rights and the Court of Justice of the EU. Tăbușcă (2012) points out that the gradual evolution in this area has been accompanied by the institutional strengthening of judicial control over compliance with legal standards.

The criminal law dimension of the EU integration processes has become another vector of its legal evolution. In particular, Chaves (2012) describes how the extension of the EU's jurisdiction to the field of criminal law was a response to transnational challenges, forming mechanisms for cooperation in combating “Eurocrime”, considering fundamental human rights.

Thus, the combination of scientific approaches allows us to assert that the EU legal system is a hybrid phenomenon that has features of both supranational and domestic legal systems, and is based on the principles of functional adaptability, legal autonomy and multi-level law enforcement. Its evolution leads to a constant transformation of institutional design, sources of law and the system of legal principles, which requires further interdisciplinary research for deeper theoretical understanding and practical improvement.

3. MATERIALS AND METHODS

The study uses a combination of generally accepted methods of legal science, in particular, the method of synthesis to combine different theoretical approaches and concepts of European integration in order to form a holistic view of the evolution of the EU legal system; institutional and legal analysis to study the content of the founding treaties, case law and acts of EU institutions; historical and legal method to study the stages of transformation of the legal system in the context of integration processes; method of systematization to organize the key stages of development.

The source base of the research is interdisciplinary materials, including the founding treaties (European Parliament, 1957, 1986, 1992, 2009), judicial precedent (Court of Justice of the European Union, 1963, 1964) and official EU documents (Council of the European Union, 1995, 2017, 2024; European Commission, 1985, 2021, 2025a; European Parliament, 2025).

4. RESULTS

The evolution of the EU legal system demonstrates a consistent complication of the legal mechanism of integration – from intergovernmental agreements within the European Coal and Steel Community to the creation of a complex supranational legal system with its own jurisdiction, principles of direct effect and supremacy. The author identifies five key historical stages: founding (1950s), institutional deepening (1960s-1980s), EU formation (1980s-1990s), consolidation and reform (1990s-2010s), and modern (2010s-present) (Figure 1).

Figure 1Visual summary of the historical stages of the evolution of the EU legal system 

Source: compiled by the author based on History of the European Union 1960-69, Council of the European Union (1995; 2024), Electoral Commission (2016), EU Neighbors East (2024), European Central Bank (2002), European Commission (2021; 2025a,b), European Parliament (1951; 1957; 1965; 1986; 1987; 1992; 1997; 2001; 2009; 2025).

Each of the identified five key stages reflects a consistent complication of legal regulation mechanisms and strengthening of the integration model. In particular, the founding stage aimed to create a legal framework for cooperation between member states, laying the foundation for a unified regulatory system. The institutional deepening stage was aimed at forming an independent EU legal order, introducing the principles of direct effect and the supremacy of EU law over national legislation. The third stage (EU formation) consisted of expanding the scope of regulation, consolidating the political dimension of integration and legalizing the Union as a supranational structure. The fourth stage, which consisted of consolidation and reform, was aimed at strengthening the effectiveness of institutions, adapting the legal system to new challenges, and ensuring a balance between EU enlargement and the functionality of its legal mechanisms. The current stage is characterized by the desire for flexibility and adaptability of the legal system, strengthening of its digital, security and geopolitical dimensions, as well as the EU's ability to respond to crises and changes in the global context. It is proposed to consider these in more detail with a focus on their normative content and institutional changes.

The formation of the EU with its special legal architecture was the result of gradual economic, political and legal integration on the European continent. One of the driving forces of this process was the pacifist movement, which, having experienced the horrors of two world wars, insisted on the unification of European states on the basis of peace and cooperation. Even within the League of Nations, there was an advisory commission that studied the possibility of creating a European union.

However, the real impetus for formalized integration came only after World War II, in the second half of the 1940s, when political leaders of the leading European countries began to advocate the creation of superpower associations that would promote stability, reconstruction, and security in the region. In particular, France, fearing the resumption of Germany's military potential after the Allies' control over West Germany was reduced, actively promoted the idea of integration. In 1950, French Foreign Minister Robert Schuman put forward a proposal to establish a shared intergovernmental organization to oversee the coal and steel sectors. This initiative, known as the Schuman Plan, laid the groundwork for the formation of the first European community – the European Coal and Steel Community (ECSC).

The ECSC was officially created through the signing of the Treaty of Paris in 1951 by six Western European nations: France, West Germany, Italy, Belgium, the Netherlands, and Luxembourg (European Union, 1951). The core objective was to delegate key regulatory powers over coal and steel production to supranational bodies, thereby diminishing the chances of another armed conflict in Europe. The legal model of the ECSC envisaged a combination of two approaches: on the one hand, centralized control over pricing, state support, investment policy, trade tariffs and production structure; on the other hand, the creation of a free trade area without significant interference from national governments. This combination reflected, in particular, the French principle of dirigisme (i.e., its focus on a policy of active intervention in the management of economic processes by the state).

Thus, the foundational stage, as depicted in Table 1, is characterized by the initiation of legal integration based on intergovernmental agreements; where the main goal is to establish a contractual framework for economic cooperation. The legal system was focused on the creation of a common market in certain sectors (primarily coal and steel), and the functioning of institutions was based on cooperation between states without a pronounced supranational element.

The institutional system of the ECSC included an independent Supreme Court, Council of Ministers, Assembly and Court of Justice. The supranational nature of this structure was manifested in the fact that the members of the Supreme Body acted independently of their states, had no right to receive instructions from governments and could not be subject to political pressure, which was clearly stated in Article 9 of the Paris Treaty, although the concept of “supranationality” was not legally defined (European Commission, 1951). However, in 1967, this article was repealed, and the term “supranational” disappeared from the official terminology of the European Communities. At the same time, the basic principles of governance laid down in the treaty did not undergo significant changes until the expiration of the Paris Treaty in 2002. After that, the legal regulation of the coal and steel sector was transferred to the EU Treaty. The effective operation of the ECSC paved the way for the establishment of two additional communities in 1957: the European Economic Community (further – EEC) and the European Atomic Energy Community (Euratom). The signing of the Treaties of Rome marked the beginning of a new phase in the European integration process. Among the three organizations, the EEC had the broadest powers - it became the basis for the economic, social, legal, and political integration of the member states. Unlike the EEC and the Euratom, which covered specific sectors, the EEC was engaged in comprehensive regulation of the internal market and the development of integration processes on a larger scale (European Parliament, 1957).

Although the objectives of European integration and the approaches to achieving them were grounded in a shared ideological foundation, the legal mechanisms outlined in the Rome Treaties differed notably from those in the Paris Treaty. Specifically, the Treaties of Rome served as foundational legal frameworks, establishing broad legal principles and outlining procedural rules essential for the operation of the European communities. Due to political expediency, the text of these treaties did not use the term “supranational”, and the role of the central body with rule-making powers, as it was in the ECSC, was transferred to the executive bodies – the Commissions. Instead, the main legislative functions were transferred to intergovernmental institutions in the form of Councils of Ministers. This change in the structure of power was not only a consequence of political considerations, but also of legal realities: the experience of the functioning of the ECSC Supreme Body has demonstrated the limited effectiveness of its decisions. National executive bodies often ignored resolutions adopted without their participation, considering them contrary to the interests of the member states. Thus, in Western Europe, two separate models of legal regulation of integration processes have gradually emerged. The first is the supranational model of the ECSC, which provided for the delegation of significant legislative powers to a central body representing common regional interests. The second is the intergovernmental model of the EEC and Euroatom, in which rulemaking functions were concentrated in the hands of national representatives in the Council of Ministers, which allowed for more effective defense of state interests.

Therefore, during the phase of institutional consolidation – focused on establishing consistent legal enforcement across the Communities – the groundwork for a supranational legal system is being laid. At the same time, the authority of the Court of Justice of the European Union is expanding, reinforcing the doctrines of direct applicability and the primacy of EU legislation over domestic legal systems. The institutions of the European Communities are acquiring more defined powers, which gradually changes the balance between intergovernmentality and supranationality.

From the outset of the existence of three distinct European communities, efforts were undertaken to unify them (Table 2). This process led to the gradual establishment of shared institutions: the Assembly and the Court in 1957, followed by the creation of the Council and the Commission in 1967. However, the specific authority and responsibilities of each institution were still governed by their respective founding treaties. By the mid-1960s, the initial stage in developing the legal architecture for European economic integration had reached completion. This framework was grounded in three foundational agreements – the Treaty of Paris and the two Treaties of Rome – as well as four principal institutions shared by all three communities: the Council, the Assembly, the Commission, and the Court of Justice (European Parliament, 1957).

During this period, the Treaty establishing the European Economic Community emerged as the cornerstone of integration, guiding the legal development of the broader unification process. In contrast, the treaties founding the ECSC and Euratom played a complementary role. The Court of Justice of the European Communities confirmed this legal hierarchy in landmark cases such as Les Verts (№ 294/83) and Costa v. ENEL (№ 6/64), describing the Treaty of Rome as “a constitutional charter of the Community founded on the rule of law” (Court of Justice of the European Union, 1963; 1964). Furthermore, the foundational role of the Treaty of Rome is evident in the fact that most EU legal branches and institutional structures were derived from its provisions. Even though the majority of EU regulations were issued by its institutions, it was the Treaty that provided the legal basis for the validity of their decisions.

Periodically, the founding acts were amended to guarantee the continuity of integration development. One of the most significant steps in this direction was the adoption of the Single European Act (SEA) in 1986, which entered into force on July 1, 1987 (European Parliament, 1986; 1987). It was preceded by extensive research initiated by the European Commission, which revealed a slowdown in economic progress within the Community against the backdrop of stronger competitors from the United States and East Asia. The 1985 White Paper identified the main obstacles to the formation of a common market, including: physical (customs, sanitary, statistical barriers), technical (differences in standards) and fiscal (tax rates, excise duties) (European Commission, 1985).

The Single European Act introduced and solidified the notion of the internal market, which was first officially outlined in Article 8a of the EEC Treaty as an area free of internal frontiers, guaranteeing the unrestricted movement of people, goods, capital, and services (European Parliament, 1957). The goal was to remove all obstacles between member states by the conclusion of 1992. In addition, the SEA significantly expanded the Community's competences to new areas: environmental protection, health, labor safety, science and regional development. Article 102a was also new, setting the direction for the creation of an economic and monetary union (European Parliament 1986; 1987).

Significant changes affected the institutional structure. The legislative role of the European Parliament was strengthened with the implementation of the common position procedure, granting it greater influence in the lawmaking process. Moreover, the range of policy areas in which the EEC Council could adopt decisions by qualified majority voting, instead of requiring unanimous agreement, was broadened. The Commission also received additional executive powers. The structure of the community officially enshrined the existence of the European Council, the highest political body that brought together heads of state and government. These changes were aimed at accelerating the formation of the EU internal market, and in practice, it yielded tangible results: the legislative process was significantly intensified, new acts appeared in areas that had previously been blocked – banking, transportation, insurance, intellectual property, and taxation.

Thus, the formation stage is marked by the transformation of the Communities into a full-fledged European Union and aims to create a single legal space with multi-vector integration. The scope of legal regulation is expanded beyond the economy to include issues of common foreign policy, home affairs and justice.

In the early 1990s, most of the provisions of the White Paper were implemented, allowing for the next stage of integration – the formation of a full-fledged European Union. The substantive core of the document, which covered about three hundred normative and regulatory measures, was aimed at removing internal barriers to the four freedoms – movement of goods, services, capital and labor – which implied not fragmentary deregulation, but comprehensive legal harmonization, standardization and mutual recognition of national regimes.

In practical terms, the implementation of the White Paper's provisions involved the elimination of physical barriers within the Common Market, which was expressed in the elimination of customs control, reduction of administrative procedures at the borders, and the creation of unified rules for the cross-border movement of goods. No less significant was the regulatory convergence of technical regulations, which ensured the synchronization of standards and the introduction of the principle of mutual recognition of certificates of conformity, which greatly facilitated the functioning of enterprises within the integration space. At the level of fiscal regulation, unified regimes for value added tax and excise taxes were created, which eliminated discriminatory tax practices between member states.

A separate set of implemented provisions concerned the services sector, in particular the financial sector, where the free provision of banking, insurance and investment services was ensured on the basis of licensing in one Member State with the right to operate throughout the Community. In the field of labor mobility, mechanisms for the recognition of professional qualifications were introduced, and the institutional framework for full liberalization of capital movement was laid, culminating in the complete removal of currency controls by the early 1990s.

In addition to purely economic and legal aspects, the implementation of the White Paper was accompanied by a set of flanking policies aimed at strengthening social, regional, scientific and innovative convergence. Institutionally, this was manifested through increased funding from the Cohesion Funds, implementation of structural adjustment programs for less developed regions, and initiation of R&D programs within the framework of the Community's research initiatives.

According to an analytical report by the International Monetary Fund (futher – IMF) of April 1992, the European Commission submitted 282 legislative proposals to the Council under the program of completing the internal market. Of these, as of mid-1992, more than 90% of the measures had already been approved at the community level, while about 75% of the directives had been implemented in the national legislation of the member states (International Monetary Fund, 1992). This significant legal and regulatory advancement set the stage for the signing of the Maastricht Treaty in 1992, which represented a shift from an intergovernmental approach to a comprehensive political Union featuring a unified currency, EU citizenship, and a coordinated foreign policy. The implementation of the White Paper was thus not only an administrative and institutional reform, but also a historic shift in the paradigm of European integration. In view of this, authors note that the vast majority of the provisions set out in the 1985 White Paper of the European Commission on the completion of the internal market were not only formally implemented but also provided real structural changes in the institutional and regulatory framework of the European Economic Community.

The signing of the Treaty on European Union on February 7, 1992, in Maastricht was a fundamental step in the legal evolution of the integration formation, which had previously functioned as the European Economic Community (European Parliament, 1992). For the first time, the concept of “European Union” was officially enshrined in the legal field, which had previously had only a political meaning (first recorded during the Paris Conference in 1972). The Treaty came into effect on November 1, 1993, marking the beginning of a more profound integration among member states and creating a multifaceted structure of the EU, commonly referred to in academic circles as the “three-pillar model.”

The first pillar encompassed the European Communities—namely, the ECSC, Euratom, and the European Community (the new designation for the former EEC). This pillar maintained the supranational nature and ensured legal continuity at the core of EU integration. The second pillar focused on the common foreign and security policy, which, being intergovernmental, shaped unified positions in international affairs. The third pillar governed cooperation in justice and home affairs, an area that grew increasingly significant due to emerging security and migration issues. Consequently, the Maastricht Treaty also set the course for completing the single internal market, which corresponds to the fourth stage of economic integration in Balassa’s framework, while also establishing the legal foundation for creating an economic and monetary union, representing the fifth stage of integration.

Thus, it was during this period that the EU significantly expanded by joining new countries, strengthened its institutional decision-making mechanisms, and revised the key treaty framework for its functioning. Successive stages of enlargement, the adoption of a number of fundamental treaties, and adaptation to global challenges have formed a qualitatively new legal landscape within the Union. Therefore, Table 3 presents the chronological sequence of key decisions at the stage of EU consolidation and reform that affected the structure, competence and geography of the EU.

Ratifying the Amsterdam Treaty (1997), which went into effect on May 1, 1999, was the next important step (European Parliament, 1997). It updated the Maastricht Treaty's provisions significantly, especially those pertaining to freedom, security, and justice, and it modified institutional mechanisms to meet the new challenges of the EU. The Amsterdam version strengthened the social component of the EU and made the first attempts to expand the scope of decisions made by a qualified majority.

The actual entry into force of the Schengen Agreement was a significant milestone in the context of free movement of people. The Schengen area, which until 2011 covered 26 countries (including twenty-two EU member states and four associated states – Iceland, Liechtenstein, Norway and Switzerland), did not include the United Kingdom and Ireland, which retained control at their borders (European Commission, 2025a). The new entity became a model for the practical realization of freedom of movement within an integrated space.

The Treaty of Nice, which was signed in 2001 and entered into force in 2003, reorganized the voting in the EU Council and altered the mechanisms of institutional functioning in anticipation of the Union's inevitable expansion. It was Nice that became a transitional stage in the EU's adaptation to new demographic, economic and political realities (European Parliament, 2001).

On January 1, 2002, the process of introducing a single EU currency, the euro, was completed, replacing the national currencies of twelve countries. This step was the culmination of a long-term course toward the creation of an economic and monetary union, which was laid down in the Maastricht Treaty. The introduction of the euro into circulation, after the non-cash phase (1999), had not only economic but also political and legal significance, in particular, a new common identity of the Euro area was established (European Central Bank, 2002).

The most significant expansion occurred in 2004, when ten countries from Central and Eastern Europe simultaneously joined the EU. This event highlighted the Union’s appeal as a symbol of stability, the rule of law, and democracy. That same year, the draft of the European Union Constitution was created to consolidate and harmonize all existing treaties. However, the ratification process was delayed after unfavorable referendum outcomes in France and the Netherlands in 2005.

In response to this constitutional setback, the Lisbon Treaty was signed on December 13, 2007, and came into effect on December 1, 2009. While it did not establish a new community, it fundamentally transformed the EU’s institutional framework: it introduced a permanent President of the European Council, founded the European External Action Service, enhanced the legislative powers of the European Parliament, and granted legal force to the EU Charter of Fundamental Rights. Additionally, the adoption of the "double majority" voting system within the Council of the EU ensured more efficient decision-making while preserving a balance between larger and smaller member states (European Parliament, 2009).

The most recent enlargement occurred in 2013 with Croatia’s accession, increasing the EU’s membership to 28 countries. Meanwhile, on June 23, 2016, the United Kingdom held a referendum in which voters chose to leave the EU, marking the first-ever case of a member state withdrawing – a process now known as “Brexit.” This event highlighted the need to reconsider the integration framework and the balance between supranational authority and national sovereignty. The referendum results showed that 51.9% supported leaving the EU, while 48.1% wished to remain. Notably, the majority of voters in Scotland and Northern Ireland favored staying in the Union, whereas most in Wales and England (except London) opted for departure. Despite the regional differences in voting, the outcome stood, and the UK’s formal exit from the EU – including all its territories – was finalized on January 31, 2020 (Electoral Commission, 2016).

Thus, the legal system of the European Union has evolved from intergovernmental coordination within the economic community to a complex multilevel supranational structure with a developed legal, institutional and political structure. This process reflects not only the growth of integration, but also the dynamics of the EU's response to internal and external challenges, transforming the Union into a political and legal entity of a global level.

The defence dimension deserves particular attention in this context. The idea of a European defence capacity was already present in the Pleven Plan of 1950, which proposed a European army under supranational authority and a common budget, but the failure of the European Defence Community postponed this issue for decades. It was reconsidered only gradually, especially through the Amsterdam Treaty and the incorporation of the Petersberg tasks, while the current geopolitical situation has made defence one of the priorities of the EU’s political and legal development.

The current stage of the evolution of the EU legal system (Table 4) is characterized by a clear trend of transition from an economic integration model to the creation of a true political and legal supranational structure capable of acting in the face of global challenges – security, technological transformation, enlargement and digitalization. The first significant step towards ensuring global security was the introduction of PESCO (Permanent Structured Cooperation in the field of security and defense). On December 11, 2017, the Council of the EU adopted a decision (CFSP 2017/2315), establishing the first projects for joint military capacity building on the basis of legally binding norms in accordance with Articles 42(6) and 46 of the EU Treaty and Protocol No. 10 thereto (Council of the European Union, 2017). This was the impetus for the formation of a unified legal framework in the defense sector, integrating 26 member states into a system of joint budgeting, planning and operational cooperation. However, a partial reversal in the legal dynamics was the official withdrawal of the UK from the EU on January 31, 2020 (Electoral Commission, 2016). This led to an act of compulsory revision of the acquis communautaire, raising questions about the legitimacy of the previous legal regimes and the protection of citizens' rights – economic and political – in relation to borders and the jurisdiction of the ECtHR.

The establishment of the Commissioner for Defence and Space marks one of the most politically significant changes of the current stage. It demonstrates that defence is no longer treated only as an intergovernmental or external policy issue, but is gradually entering the sphere of supranational coordination, industrial planning and legal regulation. This shift is reinforced by the White Paper for European Defence – Readiness 2030, which frames defence readiness as a strategic priority for the Union.

No less significant was the entry into force on May 1st, 2021, of the EU-UK Trade and Cooperation Agreement (SAFE Pact, Readiness 2030), which established a new legal framework for interaction with the status of third countries and, in particular, continued to regulate customs, competition, and human rights. This regulated a new format of integration and legal cooperation (European Commission, 2021). In parallel, on June 1, 2023, the Unified Patent Court (UPC) was launched, and, therefore, after the ratification of the agreement on February 17, 2023, the court began to function as a supranational body in the field of intellectual property. The UPC provides for legal unity of patent jurisdiction, allowing for uniform patent protection through the ECtHR (European Commission, 2025b).

The European Artificial Intelligence Act (EU AI Act) was the constitutional precedent for the current stage of evolution of the EU legal system. It was authorized by the European Parliament on March 13, 2024, and the EU Council on May 21, 2024, and it came into force on August 1, 2024. This act is the world's first regulatory complex that legally obliges artificial intelligence developers to comply with the requirements of transparency, security, and responsibility; and, as a result, fills the acquis communautaire with new digital legislation. Also in 2024, the Council of Europe Framework Convention on Artificial Intelligence was signed, which, in addition to ethical ones, sets out mechanisms for cooperation between national and European institutional legal regimes on artificial intelligence (Artificial Intelligence Act, 2024).

In 2022-2023, Ukraine and Moldova were officially granted the status of candidate countries for EU membership. This decision was made by the European Commission on November 8, 2023, and approved by the European Council on December 14, 2023. The acquisition of candidate status by the countries involved in a prolonged armed conflict with the Russian Federation is the beginning of the legal adaptation of national legal systems to the acquis communautaire and accession negotiations. Ukraine's inaugural intergovernmental conference was conducted on June 25, 2024 (EU Neighbors East, 2024). At the same time, the fulfillment of economic criteria for membership, in particular the Maastricht criteria, is of key importance for further progress on the path of European integration. As Petrukha et al. (2024) notes, excessive and prolonged budget deficits, as well as rapid growth of public debt while slowing GDP growth, can become factors of macroeconomic destabilization, in particular, cause a recession or a new crisis. Thus, ongoing integration into the EU requires legal and policy changes, along with the implementation of clear fiscal regulation mechanisms aimed at strengthening the state's fiscal capacity.

The EU's decision to withdraw from the Energy Charter Treaty on June 28, 2025, indicates reorientation towards energy independence and a transition to a new environmental legal architecture (Council of the European Union, 2024).

In 2025, the EU expanded cooperation with its allies: a defense pact was signed with Canada (SAFE Pact and Readiness 2030) and a decision was made to directly finance defense procurement through the EU budget, which means the creation of a single legal mechanism for budget support for defense infrastructure and strengthening the strategic autonomy of the Union (European Commission, 2025c).

Thus, the current stage of the evolution of the EU legal system is characterized by a clear transition to a model where supranational institutions are able to respond to global challenges through new legal instruments - defense, digital, technological and expanded institutional membership. This allows the EU to transform from an economic union into a self-sufficient political and legal community with its own norms, judicial system, security instruments, and foreign policy strategy in international law.

5. CONCLUSIONS

The European Union's legal nature is the outcome of a protracted evolution - from intergovernmental cooperation of six states to a unique supranational entity with a developed institutional architecture, autonomous legal system and strategic political subjectivity. The study shows that the development of the EU is not limited to the formal stages of the founding treaties, but reflects deeper transformations in the understanding of the very phenomenon of united Europe as a community of law, values, and political will.

The European Union has gone far beyond the classical model of an international organization. Its legal system today functions as an independent source of norms that have direct application and priority over the national law of its member states. At the same time, the legal nature of the Union remains dynamic: it is transformed in response to challenges, both internal (crises of trust, enlargement, institutional asymmetry) and external (geopolitical tensions, the war in Ukraine, the digital revolution). This flexibility demonstrates the EU's ability to act as a new type of entity - legal, but also political, strategic, and even civilizational.

Thus, the EU legal system has evolved from an economic instrument into a self-sufficient political and legal community with its own jurisdiction, democratic control mechanism, and ability to respond to the challenges of global security, digitalization, and enlargement. Also, its semiotics, institutional flexibility and multilevel legal interaction are promising areas for further in-depth interdisciplinary research.

Therefore, the modern stage of EU legal evolution shows not only the continuation of legal integration, but also the strengthening of the Union’s political subjectivity. The return of defence to the centre of the integration agenda — from the unresolved legacy of the Pleven Plan and the Amsterdam Treaty to the creation of the Commissioner for Defence and Space — confirms that the EU is increasingly developing as a security-political community.

Thus, the legal nature of the EU will continue to evolve in the direction of strengthening its strategic autonomy, institutional flexibility and ability to respond to new challenges. The role of the Union as a global actor capable of shaping normative approaches in the areas of digital technologies, climate security, defense, and geoeconomics will grow. Obviously, EU enlargement, including the potential accession of Ukraine and Moldova, will require updating legal approaches to integration, balancing between unification and preservation of the national identity of member states. The digital transformation of European law will also deepen which will contribute to the emergence of new forms of legal interaction at the level of both institutions and citizens.