The lattice model proposed by Denning in her seminal work provided secure information flow analyses with a uniform intuitive mathematical foundation. Different organisations, however, may employ quite different security lattices. In this talk, we present a framework that permits different organisations to exchange information while maintaining both security of information flows as well as their autonomy in formulating and maintaining security policy. This prescription provides a formal framework for establishing secure information flow across autonomous interacting organisations. Our work has the merit of being simple and intuitive, and is based on a rigorous mathematical framework. We show that our formulation is semantically sound, by showing that the connections we propose preserve standard correctness notions such as non-interference.