The International Union for Conservation of Nature (IUCN) Red List of Threatened Species (red list) is of fundamental importance for nature conservation and biodiversity protection. I considered the interaction between the red list and international biodiversity law (IBL), the legal regime that aims to protect biodiversity at a global level. The red list is deeply embedded in each of the five global biodiversity treaties. As the most authoritative database on species conservation status, the red list often displays a supra-legal character: its species designations effectively dictate policy makers to act accordingly. In some cases, species designations even create legal facts, a phenomenon I call auto-legality. The entanglement between the red list and IBL makes pertinent the negative critique of the list regarding species bias and interhuman inequalities. The IUCN sets rigorous assessment criteria but refrains from directing who makes the assessments. This results in the red list containing a bias in favor of vertebrate species and a Global North ecovision. Addressing these persistent problems would improve the merit of the close relation between the IUCN Red List and IBL. Species experts must come to terms with the political nature of their work and use it to the benefit of species conservation. Policy makers should invest in a better understanding of the IUCN Red List to optimize its potential for legal species protection.
