This paper proposes a blockchain-enabled audit trail architecture integrated within CivicSys AI, a privacy-preserving Management Information System (MIS) designed for U.S. public-sector agencies. By leveraging permissioned blockchain networks, smart contracts, and immutable event logging, the system ensures transparent, tamper-resistant auditability of data access, AI model updates, and compliance decisions. The architecture supports legal mandates under HIPAA, FERPA, FISMA, and Executive Order 14110, while enhancing institutional accountability and regulator-facing transparency. Simulated evaluations demonstrate that the blockchain audit layer operates efficiently at scale with minimal overhead, offering a scalable pathway for secure and trustworthy AI adoption in government-managed digital systems.