The question of how to legitimize authority is generally addressed with reference to Raz’s service conception of authority. Yet, his functional explanation does not concern itself with how authoritative institutions are empowered at the outset. Even though Raz’s monistic account of authority is coupled with input legitimacy and pluralized with Waldron’s analysis of the inter-institutional allocation of authority, it does not assist us in inter-legal situations. As inter-legality is a theory oriented towards finding legitimate ways of legal intersection, this article aims at showing how authorities between different legal orders may engage in a legitimate relationship. In doing so, it benefits from Roughan’s pluralistic and relational account of authority coupled with a conjunctive justification thesis.