European Enlargement and Rule of Law Conditionality

Scholars debate what drives European Union (EU) enlargement. On one side of the debate are those that see such decisions as based on enlargement politics of candidate and member states (Schimmelfenig et al. 2002) and others who see the decisions based on potential members’ progress on themes related to the Union’s core values of democracy, human rights, and the rule of law. There are also those, especially lately, that highlight the role of geo-politics, focusing on the influence of Russia’s invasion of Ukraine as a driver of recent enlargement. We build on European integration literature and ask: What drives EU enlargement? By answering this question, we add to this debate by closely analyzing trajectories of progress on EU core values leading to decisions about EU candidacy and membership across 23 countries and four enlargement waves (roughly from 1996 to 2024 ). Building on longitudinal data and panel data analysis, we find that progress on the core values varies considerably depending on which era of enlargement the country seeking candidacy or enlargement finds itself and that improvements on core variables do not necessarily precede favorable decisions. Our study contributes to the ongoing debate about the drivers of EU enlargement putting it into a longer historical context and comparing the effects of the drivers that received attention lately, such as geopolitics, with the effects of other factors highlighted in related literature.