Across a range of policy domains, the EU faces the challenge of balancing uniform regulation with the need to accommodate legitimate diversity among member states. Uniform rules are essential to prevent regulatory arbitrage, ensure a level playing field, and foster market integration. However, the diverse socio-economic conditions, institutional frameworks, and political preferences across member states demand flexibility in implementation to maintain social acceptance and legitimacy.

These contrasting pressures challenge established approaches such as differentiated integration, differentiated implementation, and experimentalist governance to accommodate diversity. This paper, drawing on a comparative analysis of four key regulatory domains—electricity, banking, pharmaceuticals, and competition—argues that the EU is addressing this dilemma through a more structured experimentalist governance architecture. This approach combines synchronic uniformity with diachronic revisability: uniform rules are applied across the EU but are continuously developed and revised through an inclusive review of local implementation.