In order to successfully exercise their mandate to adopt binding conservation and management measures (CMMs) for straddling and highly migratory fish stocks, regional fisheries management organizations (RFMOs) and arrangements (RFMAs) need effective decision-making procedures. The constitutive instruments of a considerable number of such bodies contain objection procedures which allow individual members to unilaterally opt-out of an adopted CMM. Most scholars and RFMO performance review panels consider that unconstrained unilateral objection procedures undermine the decision-making procedures of both RFMOs and RFMAs. This article examines the phenomenon of CMM nullification provisions, which are present in five RFMOs. Such provisions deprive adopted CMMs of their binding force for all members if a certain number of members of the RFMO object to the CMM. This article argues that there is a case for a phase-out of CMM nullification provisions together with the unilateral objection procedures to which they are closely tied. Compared to unilateral objections more generally, CMM nullification provisions raise additional legitimacy questions given that they result in the nullification of CMMs that have been democratically adopted in conformity with the legitimate decision-making procedures of the respective RFMO. This article first provides a brief overview of the rationale for objection procedures by placing the concept of objections in the broader context of RFMO decision-making. Thereafter, this article briefly examines the requirements and legal effects of individual objections of RFMO members to CMMs. The final substantive section analyzes and compares existing CMM nullification provisions, focusing on the requirements for their activation, the nature of their legal effects and the legitimacy of such procedures considering the broader decision-making procedures of individual RFMOs.