This article utilizes a novel framework to analyse the contested boundaries between law and medicine. Bringing theoretical and empirical insights together, it expands recent socio‐legal scholarship on jurisdiction. Jurisdictional analysis is conducted in an under‐researched area of health law – namely, the accessibility of trans‐related health care. The article draws upon the first qualitative research project to assess the impact of self‐declaration of legal gender status in Denmark. This was adopted in 2014, at the same time as access to hormones and surgeries was centralized and restricted. The combined impact of these reforms disappointed the trans people interviewed, which demonstrates the importance of identifying how legal and medical norms interrelate. Jurisdictional analysis helps to illuminate how law was used to develop and protect professional competencies. Such insights will be valuable for researchers interested in the potential of self‐declaration, and for scholars of health law and socio‐legal studies more generally.