Relationship-based access control (ReBAC) models define authorization policies and make authorization decisions on the basis of relationships between the entities in a system. We present a framework through which multiple ReBAC model instances can interoperate so that requests initiated in one system may target resources in a second system. Further, our framework is able to support requests passing through a chain of inter-connected systems, thus enabling many systems to be connected together or a single large system to be decomposed into numerous component subsystems. Whilst the underlying principles of this framework can be applied to any ReBAC model, we introduce its formal application to our RPPM model [3], the first, and most actively developing, general computing ReBAC model.