Although blockchains are systems that are intended to survive on their own, they still may need human intervention like other Parallel and Distributed Computing (PDC) architectures. The reasons for this intervention are twofold: management of blockchain nodes and governance of blockchain. The second focuses on sustaining blockchain unlike the first one concerning with operation of individual nodes. Proposed blockchain governance models so far include cumbersome processes in which deciding and deployment of changes rely on the involvement of multiple actors. They have been criticized from various aspects such as reducing the decentralized nature of blockchain. In this paper, we propose a novel on-chain governance model exploiting both policy-based management and decentralized identity technologies. Since it allows controlling the behavior of the system via higher level expressions that are easy to understand, the policy based management concept will fit in well with blockchain ecosystems having stakeholders from different knowledge levels. This model is not only more effective regarding existing off-chain governance models but also is simpler and more user friendly than other on-chain governance models. Besides, the emerging decentralized identity concept has the potential for solving many problems related to decision-making process of blockchain governance. By employing this concept, our approach fortifies decentralization, security and fairness while providing welldirected governance. The smart contract based modular design of our framework opens the door for adoption of its components by other governance models as well.