Spain was among the first European countries to regulate by law in 2007 women’s presence in the boards of publicly traded firms and state-owned enterprises through corporate gender quotas. This can be conceived of as a layering type of institutional change whereby new rules are attached onto or alongside existing ones through amendments, revisions or additions. In the Spanish case, the new rules have not only been rather ineffective, with only a slow and relatively meager feminisation of corporate boards having been achieved, but they have been gradually deinstitutionalised. How did this happen? This paper argues that the deinstitutionalization that occurred at the agenda-setting stage is explained by the strong veto power of status-quo actors, including businesswomen, and the diverging interpretations of the problem and solution change actors held when the new rules were introduced. The formers’ resistance yielded a weak institutional configuration based on voluntaristic action and absence of sanctions that paved the way for a poor implementation of quotas. This notwithstanding, the scant progress in women’s presence in the boards, and the learning produced during such ineffective implementation process has triggered an alignment of change actors’ strategies, thereby empowering business women to embrace the institutional goal of parity in corporate boards by recasting ideas of meritocracy and by building new alliances. The paper, developed within the Gender Equality Policy in Practice (GEPP) research network, draws on the literatures of gender-equality policy implementation and feminist institutionalism, and it adopts a multi-method empirical approach – including policy process-tracing, content analysis of policy documents, and interviews to key actors.