Today's libraries provide a broad and diverse range of resources, from books to videos and databases, and sharing conditions for each depend on modality, source, and mode of usage. In this paper, we introduce and discuss a flexible, semi-automated mechanism to assist in setting policies and tracking their implementation based on the Secure Content Exchange Negotiation System (SCENS). We consider how SCENS can be extended and applied to libraries, including as a tool for reconciling multi-institutional or multi-national policies. We also show how monitoring of SCENS negotiations can help set library sharing policies and resolve future conflicts by tracking the evolution of sharing agreements.