Corporate requirements for modern slavery-type risks in global supply chains, have gained increased attention in recent years. Limited research however has sought to address the context-relevant implications of the contractual mechanisms used to distribute and 'enforce' such requirements. In particular, the socio-economic and cultural factors that underpin and facilitate modern slavery and how these inform supplier and worker choices, have not been addressed by prior SCM scholarship. Ensuring suppliers meet modern slavery requirements, in ways that create legitimate change in the sub-tier environment, remains a complex problem that remains unresolved. For modern slavery type exploitation, the suppliers most at risk of violation exist in the sub-tiers, and in operating environments culturally removed from western-headquartered ideologies. We interviewed 36 executive level Purchasing Directors, from medium to large size firms with headquarters in Australia, the US and Finland. We employed agency and construal level theories to frame our analysis. Overall, several themes emerged regarding the limitations of the principal-agent relationship to address modern slavery risks at a supply chain scale, that reflect significant social, hypothetical and spatial psychological distance between principals, and agents. Importantly, our research drew out a range of significant themes surrounding the conflicts purchasing executives face when attempting to align western policy with complex global operating conditions, and the actual workers they seek to support. Our study sheds light on the challenges of agency theory and highlights the complexity of operationalizing modern slavery type requirements in global supply chains.