Environmental justice has become one of the most influential principles of contemporary international environmental law. Traditionally, it has focused on the fair distribution of environmental benefits and burdens, access to environmental decision-making, and the protection of vulnerable communities from environmental harm. While these objectives remain fundamental, the accelerating impacts of climate change, biodiversity loss, marine pollution, and declining ocean health demonstrate that environmental justice requires a broader jurisprudential foundation. Existing legal frameworks continue to rely predominantly on State-centred governance while giving insufficient recognition to Indigenous systems of marine governance that have sustained coastal ecosystems for generations.

This article argues that Customary Marine Tenure provides an important legal foundation for reconstructing environmental justice in the twenty-first century. Rather than viewing Customary Marine Tenure simply as a traditional method of resource management, the article demonstrates that it constitutes a sophisticated legal system capable of promoting biodiversity conservation, ecological stewardship, climate resilience, sustainable ocean governance, and community participation. It further argues that environmental justice cannot be fully achieved where Indigenous marine governance remains legally marginalised despite its demonstrated contribution to environmental sustainability.

The article introduces Ocean Governance Justice Theory, developed by Happy Okundaye Oji, as an original contribution to international environmental jurisprudence. The theory argues that environmental justice should be reconstructed by recognising Customary Marine Tenure as a complementary system of environmental governance that integrates Indigenous legal traditions with contemporary international environmental law. Under this approach, justice extends beyond the equitable distribution of environmental resources to include the recognition of Indigenous legal authority, ecological stewardship, and the long-term protection of ancestral marine ecosystems.

Drawing upon international environmental law, the law of the sea, climate justice, biodiversity law, Indigenous legal traditions, legal pluralism, and comparative ocean governance, the article demonstrates that environmental protection and Indigenous governance are mutually reinforcing rather than competing objectives. It concludes that reconstructing environmental justice through Customary Marine Tenure would strengthen marine biodiversity conservation, climate adaptation, sustainable development, and the future evolution of international environmental law.

Keywords: Environmental Justice, Customary Marine Tenure, Ocean Governance Justice Theory, International Environmental Law, Indigenous Ocean Governance, Climate Justice, Ocean Governance, Marine Biodiversity, Ecological Stewardship, Indigenous Peoples, Coastal Communities, Sustainable Development, Rights of Nature.