Ever since the peace treaties of Westphalia (signed in Osnabrück and Münster), the equal sovereignty of states is the basis of the international legal order. Various international organizations operate in this international framework, with consensus-based, weighted and qualified majority voting systems. International organizations function based on sovereignty, viewed through the lens of constitutional law (popular/parliamentary sovereignty) and international law (equal sovereignty of states). This article argues that in practice the equality of Member States of the EU is an ideal that is supported by unanimity decision-making but cannot always be fully realized due to the differences in economic and political influence of different states.

Equality of Member States and unanimity decision-making became a widely referenced topic in European public discourse. This is not unsurprising, considering the most important decisions regarding the future of the European Union have to be taken by unanimity voting in the European Council, where differing political viewpoints, national and European interests and influences of Member States collide.

International law was founded by its original legal subjects many hundreds of years ago. States with various economic and political strengths, often at war with each other and united in alliances slowly built up the practice (plus the necessary opinion juris) and international treaty corpus that led to today’s legal realities with more legal subjects and sources than ever before and with unique international entities, like the EU. One of the foundational milestones of this development was the adoption of the Treaties of Westphalia, leading to the general acceptance of the principle of equal sovereignty of states in international law.

The adoption of the UN Charter further enhanced this development, with some other universal principles codified in its founding instrument, like the principle of self-determination of peoples, the general ban on the use of force, pacta sunt servanda, peaceful settlement of disputes, and the principle of non-intervention in the domestic matters of states.

Sovereign equality is supplemented by the ban on greater states attacking smaller ones for their own interests, the self-determination of peoples makes it possible for smaller peoples to form their own states, pacta sunt servanda ensures that states with a stronger economy or military still abide by international treaties, and the principle of non-intervention ensures the protection of the constitutional order and vital national interests of states.

In the Wimbledon case, the Permanent Court of International Justice stated that states exercise their own sovereignty when they limit their rights and assume obligations for the future by signing international treaties. This can be understood in the context of the founding treaties of international organizations as accepting the decision-making rules of the international organization that the state joins.

From a constitutional law standpoint, in a parliamentary system, the people select the members of parliament who select the government; the government negotiates the treaty and handles certain steps of the accession, while the parliament ratifies it. Thus, sovereignty is practiced this way from a state’s viewpoint as well.

Still, there are different methods of decision-making that can leave more or less room for maneuver for states within international organizations considering the above-mentioned principles.  International organizations use three types of decision-making rules for non-judicial action, majoritarian, weighted voting, or sovereign equality.

Sovereign equality voting (one state, one vote), to which an example of which is the European Council, should emphasize the equality of states, however, it is not always the practice due to different economic, political and diplomatic influence of smaller, medium and larger states. The example of the WTO shows this well: according to empirical data, closing trade rounds is when hard law is generated and power-based bargaining mattered the most in those phases, while the agenda-setting takes place in the shadow of political power of states as well. Even within consensus-based decision making, sovereign equality is somewhat restricted due to asymmetrical power.

Even though states are equal under international law, they are not equal from a material power or influence standpoint. Even within the UN system, the United Nations Security Council has permanent members with veto rights, which establishes a certain hierarchy within the UN. Smaller states have less influence when it comes to negotiating international treaties and thus when it comes to revision of the primary law of the European Union as well.

In some international organizations, weighted voting systems are applied, like in the IMF, where economic size and financial participation is reflected, which is clearly reflecting economic strength. Within the Council of the European Union, qualified majority is applied where the Member States agreed to in advance by signing the founding treaties and their modifications. This leads to a tension between sovereign equality and institutional influence.

Within the European Parliament, MEPs are elected directly by the European citizens, while they take most of their decisions by simple majority. The ratio of mandates is decided by the principle of degressive proportionality, where the largest Member State has 96 mandates, the smallest 6 mandates. This system is trying to correct the lesser economic, political and diplomatic influence of smaller Member States, which could be seen as a restriction of equality of Member States, however, since the decisions are taken by a simple majority, Member States with greater influence can gather voting-alliances more easily.

Generally, unanimity favors formally the smaller Member States, while qualified majority voting for the greater ones. Unanimity mirrors the sovereign equality of states, and the Art 4 (2) TEU equality of Member States principle of EU primary law, at least formally. Meanwhile, qualified-majority voting seems to serve the purpose of being more efficient. However, in all cases, the informal influence of greater Member States is much stronger than that of smaller ones.

Equality of states therefore is a normative ideal, that can be pursued through specific decision-making formulas, however, it can never be fully achieved. Both international and European law is based on certain ideals, or myths, which can influence the further evolution of the international community.

Rules are never fully objective or neutral; they always favor one party or another. But they bring everyone to the same table.

Árpád Lapu is an assistant research fellow at the Károli Gáspár University of the Reformed Church in Hungary. He was a policy adviser on constitutional issues at the European Parliament between 2019-2024. He worked as an adviser at the Ministry of Justice of Hungary (2017-2019) and the Ministry of European Union Affairs (2024-2026), conducting EU law, international law and comparative constitutional analyses. He has earned his JD at the Pázmány Péter Catholic University in Hungary, has a BA in international relations from the University of Szeged, and an MA in European and international administration from Andrássy Gyula German Speaking University in Budapest. He has completed an LLM in international law at the Catholic University of Louvain (UCLouvain).