Japan’s leading steelmakers are increasingly marketing steel as “green” through a mass-balance approach that assigns emissions reductions to selected products without changing how the steel itself is produced. This report examines how this approach, promoted by the Japan Iron and Steel Federation (JISF), stands up against the European Union’s rapidly evolving climate and consumer-protection rules. It finds that these certificates provide no relief under the EU Carbon Border Adjustment Mechanism (CBAM) and may expose downstream buyers to greenwashing risks. As Europe tightens its rules around carbon-intensive imports and environmental claims, Japan’s current approach risks falling increasingly out of step with key export markets.