Rational institutionalism’s theoretical explanations for external Europeanisation focus on material incentives such as accession conditionality in determining change in non-EU states. However, such exogenous explanations struggle to interpret ongoing Europeanisation where accession incentives have declined or even reversed (‘stalled’ accession), but institutional adjustment still continues. This Europeanization phenomenon is evident in Turkey, a state that had actively pursued EU membership between 1999 and 2004, resulting in domestic institutional reform to align governance structures with the EU. Thereafter, Europeanisation has reversed in some policy sectors but nonetheless continued in others such as Turkish water policy, despite a declining accession process. Rational institutional arguments therefore appear to lose explanatory power for such events post-2005. An alternative theoretical proposition forwarded is that the EU accession process embedded a self-sustaining cycle of socialization through social learning around water policy norms amongst policy actors that has continued beyond this accession imperative.