Why does a signed data use agreement not stop the queries it forbids?

Federated data networks in healthcare, research, and finance rely on data use agreements to specify what recipients may do with shared data. These agreements are written in legalese and enforced after the fact through audits and legal action, not at the moment a query runs. Nothing at the data access layer checks a live query against the constraints a recipient signed up to. An ACM FAccT 2025 paper on data intermediary system design identified this gap directly: technical work on data sharing has focused on access control, meaning who can query, rather than use control, meaning what any given query may actually ask. A 2026 Royal Society paper on federated computing under sovereignty constraints confirmed that translating legal data-sharing policies into enforceable computational constraints remains an open research problem with no deployed solution.