Complex multi-actors and multi-level governance structures have emerged in areas that were traditionally exclusively the preserve of the State and treaty-making. The adoption of the United Nations Guiding Principles on Business and Human Rights (UNGP) affirmed a corporate responsibility to respect human rights to be implemented through human rights due diligence (HRDD), ie via management processes. The open-ended character of the UNGP generated the emergence of other soft instruments offering guidance to corporations in structuring HRDD. This contribution conceptualises the UNGP from the perspective of regulation as a principles-based exercise in polycentric governance reliant on regulatory intermediaries for interpretation. It then assesses the role of various sui generis normative instruments in providing interpretation to the UNGP and, how the presence of an additional layer of interpretative material contributes to the institutionalisation of responsible corporate conduct. The analysis of instruments drafted by international, non-governmental and business organisations reveals both a decentralising tension between different intermediaries due to disagreements and divergence concerning the precise extent of corporate human rights responsibilities, as well as attempts to centralise the interpretation of the UNGP. The article concludes by recommending some caution towards the employment of polycentric governance regimes and their lack of centralised interpretive authority in this domain of international law and suggests possible ways to formally establish centralised interpretation.