<p>The collaboration of autonomous and heterogeneous organizations is crucial in today’s globalized business scenario for successfully attaining common goals without sacrificing individual’s autonomy. However, the federation of services requires a flexible and robust access control mechanism that can handle heterogeneity as well as lack of trust among the separate organizational domains, leading to a number of research challenges. Even though the eXtensible Access Control Markup Language (XACML) has emerged as a widely accepted standard for formulating access control policies, its reference architecture does not support federation of access policies among multiple organizations. In addition, the migration of access policies from centralized systems to decentralized blockchain-based systems present significant obstacles due to different software stacks and execution environments. To mitigate these research gaps, we propose a middleware service to foster the automatic migration of verified anomaly-free access control policies from traditional to blockchain-based federated system. In this context, we extend the traditional XACML reference architecture to adapt the case of federated access control policies, enabling seamless policy federation and migration in a decentralized, secure, and scalable manner. We present a proof-of-concept of our proposal and the experimental evaluation on a set of benchmark XACML policies demonstrates the efficacy of the system.</p>