This paper explores the spatio‐legal dynamics of marine protected areas and their relation to socio‐environmental justice. It adopts a critical legal geography perspective to unpack ocean lawscape configurations triggered by territorial claims, the international mechanisms for maritime boundary‐making, and state sovereignty instruments. It is empirically focused on the Seaflower marine biosphere reserve, a protected area amid a geopolitical contestation between Nicaragua and Colombia in the southwestern Caribbean. By analysing its spatio‐legal history over two decades (2000–2021), the paper sheds light on the marine legalities of this region, which are often contradictory and overlapping. Focusing on the marine lawscape of Colombia, it explores the relationship between protected areas and marine territorialisation, also reflecting on the governance regimes' effects on indigenous livelihoods and marine biodiversity. The paper concludes that (i) marine protected areas are regularly being disrupted, re‐bordered, and reconfigured by the international ocean regimes governing the oceans; (ii) the link between the creation and management of marine protected areas and territorial jurisdiction compromises social and environmental justice, and (iii) inclusion of indigenous legalities might enhance equity and sustainability in ocean governance.