This essay analyses the processes of policy learning and policy change in the recognition of the same-sex unions in Brazil. Throughout the world, the recent expansion of legal, political, economic and social guarantees for specific political subjects results from the contentious debate between civil society and governments on the recognition and realisation of equality rights. This phenomenon begins to receive more attention in the policy process research, since the gender and sexuality is a controversial issue, with a high intensity of interests and power struggles between allied groups and competitors inside and outside the institutional arena. In this sense, an essential matter for understanding the political outcome is to analyse the beliefs and arguments of political actors in decision-making areas. We employ the Advocacy Coalition Framework as a theoretical basis to explain the policy changes in pluralistic systems of high competition, analysing the beliefs and attitudes of interest groups that seek to influence political outcomes over time. This research follows a qualitative approach, with exploratory and descriptive purpose, and is a cross-sectional study. The investigation focuses on a case study of the decision of the Federal Supreme Court (STF), which, interpreting infra-constitutional legislation under the Brazilian Federal Constitution of 1988, to judge ADI 4277 and ADPF 132, recognised the same-sex unions in 2011. The sources of data are documents (legislation, reports, statements, speeches and news) used and produced during the policy process and that were relevant for decision making. The data are evaluated by content analysis with the support of the software of qualitative analysis NVivo 11. Based on the first analyses, we argue that the STF decision did not legitimise only a legal situation, it also had concrete and contradictory effects on the political and social life of the people. The main arguments debated in this decision-making process were: promotion of equality, non-prejudice and discrimination, protection of sexual minorities, and understanding of family. That process has broadened the framework of discussion and dispute between different views about the normality patterns of sexuality. There are a series of beliefs and strategies built by interest groups for and against same-sex unions, which demonstrate the stiff resistance on the part of society to respect this right. On the one hand, there is still a binary and hierarchical logic in the society that places genders and sexualities in different spaces and holds distinct social values. On the other hand, it is a fact that same-sex couples are an old social reality that has become a public issue in contemporary times as a matter of citizenship.
