This article – based on the case studies of the WHO and the FAO – shows that the expansion of cooperation between international organizations (IOs) and non-state actors (NSAs) leads to a significant rearrangement of IOs organizational boundaries. IOs develop bureaucratic procedures (e. g. due diligence, risk management) that lead IO employees to be in charge of “taxonomy work”, i. e. the classification and hierarchization of NSAs. This work re draws the boundaries of IOs and generates resistance and contestation, both inside and out side IOs.