One challenge in the area of supply chain management has been achieving sustainable compliance with labour rights throughout the entire production chain, including lower tiers of production. This article inquires specifically around sub-contracting, especially what is a brand's or a buyer's responsibility regarding workers' rights beyond its first tier of suppliers. In-depth literature on this issue remains scarce despite buyer's responsibility being at the core of outsourcing, the very area that brought disrepute to Nike and thus moved corporate social responsibility (CSR) in the international limelight 15 years ago. This article reviews 12 prominent CSR instruments and asks: do they provide legitimacy to calls that buyers should be responsible for labour conditions down their supply chains? Where do these responsibilities end as abuses become more remote and take place at lower tiers of the value chain? What are the concepts, the principles that attribute responsibility to the buyer company and what concepts are used to limit these responsibilities? What strategies exist to improve conditions at sub-contractor level? Reading a dozen CSR instruments with a keen eye to sub-contracting reveals a staggering diversity of answers. The responsibility of the core company, particularly the limits of responsibility, move in and out of focus. Questions around buyers' responsibilities remain open, but there is a wealth of concepts and experience to draw upon. Professor Ruggie, a United Nations Special Representative of the Secretary General, could bring clarity in this area of CSR and is invited to reconsider the justification, scope and content of a buyer company's responsibility to protect workers' rights in its value chains.