The long-standing discussion on decoupling has recently moved from adopters not implementing the agreed-upon policies towards compliant adopters not achieving the goals intended by institutional entrepreneurs. This 'means-ends decoupling' prevails especially in highly opaque fields, where practices, causality, and performance are hard to understand and chart. This paper conceptualizes the conditions under which the adoption of institutions in relatively opaque fields leads to the achievement of the envisaged goals. Voluntary sustainability standards governing socio-environmental issues illustrate these arguments. I argue that the lack of field transparency drives institutional entrepreneurs to create and maintain concrete and uniform rules, apply strong incentives, and disseminate 'best practices' to ensure substantive adopter compliance. However, such rigid institutions are ill-equipped to deal with the causal complexity and practice multiplicity underlying opacity while they smother adopter agency. The ensuing tension between substantive compliance and goal achievement leads to an inherent trade-off: institutional entrepreneurs who remedy the policy-practice decoupling may enhance the disparity between means and ends, and vice versa. While sustainability standards and other institutions in highly opaque fields can, therefore, not fully achieve the envisaged goals, the trade-off can be reduced through systemically designed institutions that promote goal internalization and contain niche institutions.