This paper examines the effects of local environmental regulation on the sourcing patterns of commodity trading firms (i.e., firms that source commodities from upstream producers and distribute these commodities further downstream). Exploiting a transparency and enforcement regulation targeting producers in deforestation-intense Brazilian municipalities, I find trading firms do not reallocate their sourcing from regulated to unregulated municipalities. However, trading firms reduce their exposure to upstream deforestation and scope 3 emissions associated with their sourcing in both regulated and unregulated locations. Although the direct effect in regulated municipalities could reflect the first-order responses by producers, the positive spillover effect in unregulated municipalities suggests trading firms actively invest in sustainable sourcing. Yet, not all firms exhibit a positive spillover effect: this effect is concentrated in trading firms exposed to stringent local enforcement actions and committed to zero deforestation sourcing. I conclude that upstream supply chain shocks can have transmission effects on agents further down in supply chains, evidenced by global trading firms adopting firm-wide sourcing strategies that can shape the efficacy of local environmental regulation.