The Openness-Equality Puzzle (OEP) confronts us with the following conundrum: How is the territorial closure of nation-states regarding immigration related to their internal equality, and how are policies regulating immigration and internal equality related to global inequality? In this paper, I introduce some key conceptual, theoretical, and empirical innovations that contribute to the solution of this puzzle. First, I introduce the OE-typology and use it to explicate how the widespread idea of an openness-equality trade-off can be located in an underlying two-dimensional policy space. I also show how the conception of this trade-off (correlations versus configurations) matters for our understanding of the OEP. Second, I introduce a specific version of the OE-typology that focuses on the openness of immigration regimes and the inclusiveness of citizenship regimes. I then connect the four typological ideal-types to normative positions prescribing different OE-configurations in light of their moral worth or consequences for equality-related goals. Third, I review how the correlational empirical trade-off assumption evolved and how it has fared in existing empirical tests, focusing on the work of Martin Ruhs. Fourth, I re-assess Ruhs’ finding that autocracies display starker OE-trade-offs than democracies when it comes to labor immigration programs. The re-analysis of Ruhs’ original data shows that this result hinges on the inclusion of specific autocracies, namely the Gulf autocracies, which have an open-exclusive boundary regime situated in an idiosyncratic national context. Fifth, using a large panel dataset, I offer an explorative empirical analysis that investigates the moderating role of the level of democracy for OE-correlations and OE-configurations. The analysis shows that political regime type neither matters for OE-configurations nor for OE-correlations as the level of democracy it is not a strong and consistent moderating variable. Overall, the openness variables (I distinguish non-economic and economic openness) do not have strong effects on the equality variable (I focus on immigrant rights and access to citizenship). The Gulf autocracies emerge as exceptional cases that display an open-exclusive boundary regime when it comes to economic and general immigration policy and a closed-exclusive boundary regime when it comes to non-economic immigration policy. I conclude that this finding leads to disturbing conclusions for both utilitarians and cosmopolitans when it comes to the OEP, but only if they are ready to compromise democratic ideals. Finally, I reflect on the implications of my analyses for our understanding of the OEP and chart some future research avenues.