From a legal standpoint, Ter Stegen is within his rights to withhold personal medical information from sharing with third parties, even governing bodies. However, Barcelona argue that the player’s refusal is in conflict with his contractual obligations, which include facilitating registration processes in extraordinary injury cases.
Barca encountered similar scenarios in the recent past, most notably with Andreas Christensen and Ronald Araujo. In both instances, the injured players provided consent for the club to submit their medical documentation to La Liga. This allowed the club to register Dani Olmo and Inigo Martínez as temporary replacements successfully.