The ASTM Additive Manufacturing Center of Excellence, in collaboration with the UK Ministry of Defence's TAMPA project, has published the 'Strategic Guide for Certification of Additive Manufacturing Parts for Defense Applications,' available for free download. This guide provides a common, part-criticality-based certification approach for defense organizations, manufacturers, and suppliers across air, land, and sea domains. It establishes a four-tier A-to-D part classification system, where certification evidence requirements are determined by safety criticality, and defines two pathways: process qualification and test certification. Evidence requirements cover raw material control, equipment and process qualification, product verification, and non-destructive testing. Positioned as nationally neutral and technology-neutral, the guide is intended for use beyond the UK, including supply chains of AUKUS and NATO allies, and represents a pre-standardization effort. This guide is a key step toward resolving inconsistencies in cross-border certification standards, offering a unified reference framework for the large-scale deployment of additive manufacturing in defense.