["Journal of Law and Society, EarlyView. ", "\nAbstract\nThe use of the Welsh language is generally understood as a ‘right’ in contemporary Wales. While this right is often lauded as one of Welsh devolution's defining achievements, the efficacy of current protections is contested. This article contributes to the debate by focusing on the prison context, where the question of Welsh language rights is particularly complex. Drawing on interviews with Welsh‐speaking former prisoners, stakeholders with experience of monitoring Welsh language provision in prison, and documentary analysis, we subject the ‘rights’ label to empirical scrutiny. We find implementation gaps in official policy across the Welsh prison estate, scepticism among former prisoners towards existing protections, and limited oversight. The article concludes that while Welsh‐speaking prisoners may have ‘rights’ in a broad sense, these rights guarantee little in practice. Entirely contingent on the goodwill of prison authorities and weakened by constitutional complexity, they are a stark reminder of Welsh devolution's limited progress.\n"]