The difficulty in engaging the engaged: administrative adaptation to the early warning system within the UK Houses of Parliament

This article applies a mixed-methods approach through semi-structured interviews and document analysis to provide a comprehensive account of administrative and behavioural adaptation within the UK Houses of Parliament (HoP) to the EU’s subsidiarity monitoring mechanism, the Early Warning System (EWS). The article also tests theoretical assumptions regarding the adaptation and use of the EWS on this basis, confirming that Eurosceptic MPs bolster the use of the EWS and finding that the HoP are an outlier among bicameral legislatures, as the lower chamber was the primary user of the EWS. Overall, results demonstrate that both the House of Commons and the House of Lords treated the EWS as an optional bolt-on when adapting to the mechanism. Furthermore, the EWS did not encourage the HoP to increase engagement with UK devolved legislatures, but the mechanism contributed to the mainstreaming of EU scrutiny in the case of the Welsh and Scottish legislatures.