Functions and optimization of soft law in the international governance of synthetic biology: The predicament of hard law vs. the rise of soft law.

Synthetic biology, as an emerging field that integrates life sciences and engineering technology, is driving profound transformations in global science, ethics, and legal systems. In international legal framework, the Biological Weapons Convention (BWC) and the Convention on Biological Diversity (CBD) have established initial hard law governance systems. However, these frameworks still face structural limitations in terms of technical adaptability, the scope of provisions, and institutional coordination. Soft law, with its flexibility, non-binding nature, and ability to build consensus, is increasingly becoming an essential supplement to the international response to the ethical risks of synthetic biology. International organizations, industry alliances, and non-governmental actors are constructing a multi-layered soft law governance network through ethical guidelines, policy recommendations, and codes of conduct, providing institutional support for risk identification, technology classification, and behavioral guidance. Soft law is well-suited to perform the roles of guiding and providing feedback in governance, while hard law should focus on the construction of systems of rights and responsibilities and the establishment of obligations. There is a collaborative governance model that integrates both soft and hard law. This model, characterized by "soft law guidance, hard law consolidation, and soft law feedback," aims to create a flexible and enforceable governance framework. This approach ensures that soft law provides a timely and adaptive starting point, hard law offers a uniform and accountable foundation, and a feedback loop allows for continuous adjustment based on practical experience.