This paper aims to bring to light specific issues which precluded support by Norway of the Weddell Sea MPA proposal tabled to CCAMLR in 2016 by the delegation of the European Union and its Member States. We present results from Marxan and other analyses conducted for the purpose of evaluating aspects of the Weddell Sea MPA planning process which were integral to the development of the proposal, focusing on the suitability of the Marxan analysis to inform MPA border delineation and the potential impact to fisheries. We pose questions and make recommendations regarding the technical and procedural decisions made during the Weddell Sea MPA planning process, and discuss these concerns in the context of the transparency of the process, the consistency with other CCAMLR MPA planning processes, and Norway’s commitment to ensuring that any area-based management it supports is founded on a consistent and rigorous scientific basis.