Supply Chain Due Diligence in Space-based Manufacturing and Lunar Resource Extraction: Building Sustainable & Resilient Cislunar Operations

Space is moving from episodic missions to continuous industrial activity. Space-based manufacturing in microgravity and the extraction of lunar resources through in-situ resource utilisation are now anchored in engineering roadmaps and national regulations, not only in scientific aspiration. Reviews of in-space manufacturing show a steady shift toward orbital assembly lines, additive manufacturing, and on-orbit servicing as enabling infrastructure for a growing commercial space economy. In parallel, technical literature on lunar ISRU highlights water-ice excavation, oxygen production from regolith, and additive construction as prerequisites for extended lunar presence and for cheaper in-space logistics. These developments create a cislunar supply chain that loops between Earth, orbit, lunar orbit, and the lunar surface. The chain is long, capital-intensive, highly autonomous, and legally hybrid, because private operators act under state authorisation and continuing supervision under the Outer Space Treaty. At the same time, terrestrial regulation is hardening supply chain due diligence into binding law. The EU Corporate Sustainability Due Diligence Directive requires large firms to identify, prevent, mitigate and remedy human rights and environmental harms across their chain of activities, with monitoring and liability for failure. This paper is a doctrinal and conceptual study that brings these two trajectories together. It maps the cislunar supply chain, explains why due diligence has distinct features in space, benchmarks early space resource laws and soft-law standards against terrestrial due diligence regimes, and proposes a Cislunar Due Diligence Cycle with concrete benchmarking indicators for sustainability and resilience. The paper argues that due diligence can serve as a practical bridge between state responsibility, private innovation, and the long-term stewardship of orbital and lunar environments.