The restrictions and bans imposed on insecticides of the neonicotinoid family in Europe were legitimized by emerging knowledge about their impact on the health of bee populations. That such knowledge was articulated and acted upon in the regulatory space is puzzling, given the standard forms of regulatory science, and the ways in which scientific knowledge is used in this very space. This short article reviews research in social science about regulation and regulatory knowledge, to help understand how research on bee decline opened the possibility of wide regulatory restrictions on neonicotinoids.