As part of international obligations and national policies, most nations are working toward establishing comprehensive, adequate, and representative systems of terrestrial and marine protected areas (MPAs). Assigning internationally recognized International Union for Conservation of Nature (IUCN) protected area categories to these MPAs is an important part of this process. The most recent guidance from the IUCN clearly states that commercial or recreational fishing is inappropriate in MPAs designated as category II (National Park). However, in at least two developed countries with long histories of protected area development (e.g., Canada and Australia), category II is being assigned to a number of MPAs that allow some form of commercial or recreational fishing. Using Australia as a case study, this article explores the legal and policy implications of applying protected area categories to MPAs and the consequences for misapplying them. As the Australian Government is about to embark on potentially one of the largest expansions of MPA networks in the world, ensuring the application of IUCN categories is both transparent and consistent with international practice will be important, both for the sake of international conventions and to accurately track conservation progress.