In a parliamentary hearing in Brussels last month, a senior MEP posed the question that hangs over every enlargement discussion with unusual directness: “Are we seriously considering admitting countries to this union that cannot meet the standards we already struggle to enforce among existing members?” The question was pointed. The silence that followed was more revealing than any answer. EU enlargement — the process of admitting new member states — has been the bloc’s most transformative policy instrument and its most contested. The debate has never been more live than it is in 2026.
The case for enlargement
The strongest argument for enlargement is geopolitical. As the war in Ukraine has demonstrated with devastating clarity, the EU’s neighbourhood is not stable. Countries outside the EU’s framework — subject to Russian influence, Chinese investment, and the governance vacuum that comes from uncertain European futures — are vulnerable to instability that eventually reaches EU borders through migration, energy disruption, or military spillover. Enlargement is the EU’s most powerful tool for stabilising its neighbourhood, because membership provides the incentive structure — market access, institutional support, legal frameworks — that drives genuine reform in ways no partnership agreement can match.
The historical record supports this. Every previous EU enlargement has been judged, in retrospect, as a success. Central and Eastern European countries that joined in 2004 and 2007 have experienced per capita income convergence with Western European levels, democratic consolidation (with the notable and serious exceptions of Hungary and, to a lesser extent, Poland’s PiS period), and security integration through NATO membership. As explored in our Western Balkans analysis, the credibility of the membership promise is the EU’s primary tool for maintaining influence in countries that have not yet joined.
The case against — or at least for caution
The arguments for caution are also substantial. The EU’s decision-making machinery was designed for six member states; it has been adapted for twenty-seven with considerable difficulty. Adding six Western Balkan countries, plus potentially Moldova, Ukraine and Georgia in some future decade, would require institutional reforms that current EU members have consistently failed to agree. Unanimity requirements that already produce paralysis at twenty-seven become progressively more constraining as membership grows.
The rule-of-law problem is acute. Hungary’s decade-long defiance of EU democratic norms — an episode that has consumed enormous institutional energy and financial leverage — raises the question of how the EU would manage similar situations with a larger membership. The reform conditionality in the accession process is designed to prevent this, but as our analysis of the EU’s institutional architecture noted, enforcement mechanisms work better on candidates than on members.
The budgetary implications are also real. Ukraine’s agricultural sector alone would radically alter the dynamics of the Common Agricultural Policy and EU budget negotiations. Any enlargement requires either a significant increase in EU budget contributions from existing members or a reform of the policies that make membership financially significant — neither of which is politically straightforward.
Where the debate goes from here
The honest position of most European policymakers is somewhere between the two cases: yes to enlargement in principle, yes to genuine conditionality, yes to parallel institutional reform, and a recognition that the process will be slower and more complex than its advocates promise. The EU has opened accession negotiations with Ukraine and Moldova. The Western Balkans process continues to move slowly. The question is not whether enlargement will happen but when, in what order, and whether the EU’s institutional infrastructure will be reformed sufficiently to absorb new members without paralysis.
