Abstract: The enactment of the Law on Promoting the Private Economy marks a new phase in the legal protection of China’s private sector. Article 10 of the law establishes for the first time a statutory foundation for a nationwide unified market system. However, local legislation—the “last mile” in constructing this unified market—still faces numerous practical obstacles. Some local governments have surreptitiously expanded administrative licensing authority through non-standard regulatory instruments, resulting in the risk of institutional instrumentalization and involutionary competition within the market access negative list system. This phenomenon underscores deeper contradictions rooted in experimentalist reform path dependence, including inadequate central legislative supply, distortions in regional economic competition strategies, and outdated techniques in central-local legislative allocation. Introducing a collaborative central-local legislative framework offers an effective solution to these challenges, aligning the “top-down” unification of the rule of law with “bottom-up” institutional innovation, which is consistent with the legislative principle of advancing reform within the legal framework. Specifically, this framework advances a nationally unified market access regime through a balanced mechanism of incentives and constraints, countering local protectionism through legal uniformity. It employs the principle of proportionality to delineate legislative boundaries between central and local authorities, enabling differentiated implementation of central legislative mandates at the local level. Furthermore, a comprehensive oversight mechanism integrating ex post legislative evaluation with filing and review procedures strengthens the articulation of dual review systems, forming a normative closed-loop for constructive interaction between central and local legislation.