A pivotal point in time has been reached in the ongoing negotiations under the auspices of the International Seabed Authority (ISA) towards the adoption of regulations for the commercial exploitation of mineral resources in the deep seabed beyond national jurisdiction. The ISA has a mandate to ensure that activities in the Area, legally designated as ‘common heritage of humankind’, are carried out for the benefit of humankind as a whole. Yet, there is a growing sense of unease with the potential imminence of the commercial exploitation phase, and concern that the implementation of all components of the common heritage principle, including its environmental and distributive ambitions, will be compromised in the interest of a handful of industry stakeholders. This article dives under the surface of these tensions by asking how the public interest in a global commons can become constructed in a way that conflates diverse and opposing interests in favour of value extraction by the private sector, revealing the ambivalent role of international law in the process. It uses the concept of ‘false necessity’ to question the apparent urgency and inevitability of commercial exploitation, more specifically to the extent it obscures and pre-empts more inclusive conceptions of ‘benefit’ for humankind. By shifting the focus from the much-debated risks of deep seabed mining to the notion of benefit, the article illuminates the inherent contradictions and distributional asymmetries obscured by the conflated yet purportedly universal conception of public interest in exploitation.