<p>The adoption of IoT has significantly influenced supply chain systems by offering real-time monitoring and data-driven control. IoT collects sensitive information such as location, inventory, users' personal and financial details, contracts, and competitive pricing to provide efficient supply chain services. Breaches in IoT data can expose supply chain operations and create conflicts of interest, impacting decision-making. Access control has emerged as a novel approach to address these problems via data access in a permissioned manner, along with enhanced security and privacy. However, existing solutions have limitations, such as computationally intensive access policy management, data leakage and biased decision-making due to lack of <i>Conflict of Interest</i> management and static access permissions. This work proposes a blockchain-regulated Chinese wall model-based access control to address these problems. Blockchain ensures tamper-proof access log details by recording every change over a decentralized ledger. Meanwhile, the Chinese wall model prevents data leakage and provides <i>Conflict of Interest</i> management to guarantee data integrity and confidentiality. Additionally, smart contracts dynamically adjust permissions based on changes. To address the problem of expensive data storage, blockchain is integrated with IPFS. We provide a thorough security analysis of our framework by providing a threat model and formal BAN (Burrows-Abadi-Needham) logic proof. Moreover, the semantic security of the threat model is proved in the RoR (Real-or-Random) model. Furthermore, the superiority of our work is established through a security comparison and computational cost analysis with other peer models. Lastly, smart contract-based implementation through Truffle is done to analyze the framework's effectiveness.</p>