“…Moreover, studies focusing on implementation have concentrated on the number of opportunities that states have to diverge from common rules beyond the treaties. Not only can they negotiate exemptions through secondary law (Duttle et al, 2017;Franchino, 2007;Schimmelfennig & Winzen, 2020), they can also interpret rules in different ways and, consequently, implement them differently (Andersen & Sitter, 2006;Chebel d'Appollonia, 2019). Even with regards to legislation they opt in to, countries enjoying exemptions perform, on average, worse in comparison to full members (Zhelyazkova, 2014).…”