This paper analyses how retirement migrants' mobility is enabled, impeded, and sometimes enforced by national and European Union migration and welfare rules and the ways in which retirement migrants deal with these ‘legal gates’ in practice. Legal gates are conceptualised as the rules operating at different local, national, and supranational levels, which regulate human mobility between one jurisdiction and another. Drawing on the new mobilities paradigm, the paper shows how retirement migrants construct and negotiate their mobility and residence arrangements within the confines of the different welfare systems. Focusing on Dutch and Spanish retirement migrants who spent their working life in the Netherlands and move or return (permanently or temporarily) to Spain after retirement, this paper shows on the one hand the power of the state to influence retirement migrants' mobility and on the other hand it shows how inequalities between retirement migrants' socio‐economic status influences their capacity to be mobile. Copyright © 2015 John Wiley & Sons, Ltd.