The European Commission is trying to solve two problems at once as the European Union prepares for its biggest enlargement challenge in years: how to make room for new members without allowing an expanded bloc to become harder to govern, and how to prevent future members from weakening the democratic rules they were required to adopt before joining.

Its package of proposals, presented on October 6, is therefore as much about changing the EU itself as preparing Montenegro, Albania, Moldova and Ukraine - now the four frontrunners in the accession process - for membership. The Commission argues that a larger Union can be accommodated under the existing treaties, but says decision-making, safeguards, administrative capacity and the budget will all need to be adjusted.

“Europe's future depends on the choices we make today. Enlargement of our Union is a geopolitical imperative,” Commission President Ursula von der Leyen said. “Today, we are laying the groundwork to ensure that a larger Union is also a stronger one: more resilient, more effective, and firmly anchored in the values and rules that define us.”

This ambition reflects a profound change in the political context surrounding enlargement. For much of the past decade, the prospect of bringing new countries into the EU appeared remote, with governments reluctant to contemplate another major expansion after the bloc's 2004-13 enlargement and the political difficulties that followed. Russia's full-scale invasion of Ukraine in 2022 changed the strategic calculation, putting enlargement back at the centre of European security policy and giving new impetus to the accession ambitions of Ukraine and Moldova as well as the Western Balkans.

The Commission is now attempting to ensure that the geopolitical argument for enlargement does not overwhelm the institutional and political risks. Its central message is that the EU is capable of becoming larger, but that enlargement cannot simply mean adding countries to existing structures and hoping they work. The Commission's review identifies administrative capacity and implementation as recurring challenges, pointing to the need for stronger regulatory and supervisory systems, interoperable digital systems and closer cooperation between national administrations.

That is the relatively uncontroversial part of the package. The harder question is how much power existing member states are prepared to give up to make an enlarged EU functional.

The Commission wants more decisions to be taken by qualified majority voting (QMV) rather than unanimity, including some decisions during accession negotiations. That would be a significant change in practice even if it does not require wholesale treaty reform.

At present, member states retain considerable scope to block progress in accession talks. The Commission argues that allowing qualified-majority voting for the opening of negotiating clusters and other intermediate decisions could make the process less vulnerable to individual governments using enlargement as leverage for unrelated disputes. This is a logical response to an EU that could eventually have 30 or more members. The larger the club becomes, the more difficult unanimity becomes as a practical governing principle. However, the proposal runs directly into one of the EU's oldest political tensions.

Recent modelling by Think Tank Europa looks at the impact of adding Montenegro, Moldova, Ukraine and the Western Balkan countries. It concludes that Montenegro's relatively small population would have little effect on the population threshold, while Ukraine and Moldova would have a much more substantial impact. The study also finds that a Polish-Ukrainian combination could become an important component of blocking minorities.

The Commission also wants to make greater use of so-called passerelle clauses, which allow the EU to move from unanimity to QMV in certain policy areas without a full treaty revision. It has identified sanctions, tax fraud and some fiscal measures linked to energy policy as areas where this could improve the bloc's ability to act. The problem is that activating the passerelle mechanism itself generally requires unanimity.

The Commission is also looking at enhanced cooperation, under which at least nine member states can move ahead together when the EU as a whole is unable to agree. That offers a way of avoiding paralysis, but risks producing a more differentiated Union in which countries participate in different combinations of policies. That prospect is likely to be politically sensitive as enlargement advances. Some governments favour greater flexibility, while others fear that differentiated integration could leave new members with fewer rights or create an EU divided into first- and second-tier participants.

The more politically striking element of the package is the attempt to deal with a problem that the EU has struggled to resolve after accession: what happens if a country that met the criteria for membership subsequently dismantles parts of its democratic system?

The Commission proposes stronger safeguards in future accession treaties. Existing safeguards covering the economy, the single market and justice and home affairs could remain available for substantially longer after accession, while a new institutional safeguard would address serious breaches of EU fundamental values and the principle of sincere cooperation. In the most serious cases, the Commission says, sanctions could include suspension of a country's voting rights in the EU Council.

The proposal is aimed at reducing the gap between the EU's powerful ability to demand reforms before membership and its weaker ability to respond once a country has joined. The experience of Hungary and Poland under their previous governments demonstrated how difficult it can be to use Article 7 of the EU treaty against a member state accused of undermining the rule of law, particularly when political alliances allow governments to shield one another.

Enlargement Commissioner Marta Kos said the Commission wanted to give the bloc more effective tools. “Our assessment shows that the EU can accommodate a larger membership. But there are areas where we see challenges we need to address. One is the rule of law and sincere cooperation, where we are proposing stronger possibilities to prevent backsliding, including reducing funding or restricting voting rights,” she said in an interview with The Guardian and other international media on October 6.

The safeguards would be temporary, targeted and reversible rather than creating a permanent class of probationary members. That distinction will be important to candidate countries, which are unlikely to accept membership on terms that leave them permanently more constrained than existing members. It will also be important politically inside the EU. Existing governments need to be persuaded that enlargement does not mean importing new vulnerabilities into a system that already struggles to enforce its own rules.

"The EU is finally asking the right question about enlargement," writes Janis A. Emmanouilidis, director of studies at the European Policy Centre (EPC) think-tank. "It is not only what aspiring members must do to join, but what the Union itself must do to prepare for an EU30+. Yet the challenge goes further: an enlarging Union must also prepare for an era of permanent disruption."

The Commission is simultaneously proposing to make the accession process more tangible by allowing candidate countries to participate in selected EU policies before they formally join. It plans to identify opportunities in sectors including energy, transport, digital services and defence, with access dependent on progress towards EU standards and alignment with the bloc's strategic interests. Participation would be conditional and reversible, with annual dialogues used to assess progress.

Formal accession can take years, particularly for countries with large and politically difficult reform agendas. Offering incremental access to the single market and EU programmes provides Brussels with another way to reward reform without waiting for the final signature on an accession treaty. For candidate countries, it also offers something more concrete than another round of technical negotiations. Earlier access to European markets, infrastructure networks or strategic programmes could bring economic benefits while membership remains distant.

"The institution’s latest proposal doubles down on market convergence as an interim step to membership. And, to make that offer more credible, it proposes tighter timelines with target dates for accession as an add-on," writes Dimitar Bechev, senior fellow at Carnegie Europe.

"If these proposals are implemented, they will de facto create something that has been the talk of the town in Brussels lately: associate EU membership. Yet, they risk failing to convince countries such as Serbia, Turkey, and Georgia to stop hedging, turn their backs to the likes of China and Russia, and cast their lot in with the EU."

Moreover, he adds, "the issue of compliance with the union’s standards remains critical in the current proposal. Brussels has been careful to point out that market access comes with strings attached."

Still, the Commission insists that gradual integration will complement rather than replace accession. That may become particularly important for countries whose political commitment to EU membership is less clear-cut than that of the current frontrunners. The closer the EU comes to offering a menu of partial integration, the more important it becomes to demonstrate that full membership remains the ultimate destination.

Among the four frontrunners, Ukraine poses the biggest economic test for the EU budget. The Commission says enlargement can be financed while maintaining existing priorities. Under its proposed 2028-34 budget framework, candidate countries would initially receive support through the Global Europe instrument, with funding shifting into national and regional partnership plans once they join. Additional funding would become available for areas such as cohesion, agriculture, home affairs and cross-border cooperation.

But Ukraine presents a scale of economic adjustment unlike that associated with previous enlargements. Its agricultural sector is both large and highly productive, creating the prospect of substantial pressure on the EU's Common Agricultural Policy and agricultural markets if Ukraine receives the same benefits as existing members from the outset.

The Commission therefore envisages targeted arrangements that would limit financial support and market access for sensitive agricultural products while helping Ukraine regain access to traditional export markets outside the EU. That proposal illustrates the central political bargain behind the package. Enlargement has become strategically more important to the EU, but strategic necessity does not eliminate the distributional conflicts that come with bringing poorer countries, and in Ukraine's case a very large agricultural producer, into the bloc.

Similar tensions will arise over cohesion funding, labour mobility and other areas where accession changes the distribution of EU resources or market access.

The Commission's assessment is deliberately cautious. It says most of the necessary changes can be made within the existing treaty framework, avoiding an immediate attempt to reopen the EU's constitutional settlement. That makes the package more politically achievable, but also limits its reach.

The political test will now begin. The proposals must be discussed by the member states, the European Parliament and the Council, while the European Council is due to address enlargement and the bloc's internal preparations this month. The Commission can propose mechanisms for a larger Union, but it cannot force national governments to surrender vetoes, accept a leaner institutional structure or agree to new restrictions on their ability to protect domestic interests.

Enlargement is increasingly presented as a geopolitical necessity, particularly as Europe seeks to anchor Ukraine, Moldova and the Western Balkans more firmly to the European project. Yet the more urgent enlargement becomes, the more difficult it may be to postpone the internal reforms required to make it work. The Commission's proposals are an attempt to bridge that gap without reopening the treaties. Whether that is enough will depend less on the technical design of the package than on the willingness of the 27 existing members to accept that a larger EU cannot necessarily operate in exactly the same way as the smaller one they know.