UNCLOS: Framework for Maritime Law and Ocean Conservation

The oceans cover over 70% of the Earth’s surface. They regulate climate, sustain billions of livelihoods, and serve as the backbone of global trade. Yet for centuries, the lack of a unified legal framework meant that competing national claims, resource exploitation, and maritime disputes could spiral into conflict. That changed in 1982 with the adoption of the United Nations Convention on the Law of the Sea (UNCLOS) – a treaty so comprehensive it is often called the “constitution for the oceans.” UNCLOS created a rules-based order for everything from navigation rights and maritime boundaries to environmental protection and deep-sea mining. Here’s how it works and why it matters more than ever.

How UNCLOS came into being 🔗

Before UNCLOS, ocean governance relied largely on the 17th-century freedom-of-the-seas doctrine, which limited national jurisdiction to a narrow coastal belt and left everything else open to all. That principle held for roughly 300 years, but by the mid-20th century it was straining under the weight of expanding territorial claims, pollution, overfishing, and new technologies for extracting seabed resources. In 1945, U.S. President Harry Truman asserted control over continental shelf resources, prompting other nations – including Chile, Peru, and Ecuador – to extend their own maritime claims.

The United Nations responded by convening three conferences. The first, in 1958, produced four separate conventions on territorial seas, the continental shelf, the high seas, and fishing. The second, in 1960, ended without agreement. The Third UN Conference on the Law of the Sea (UNCLOS III), which ran from 1973 to 1982 with over 160 participating nations, finally produced the comprehensive treaty we know today. The convention was opened for signature on 10 December 1982 in Montego Bay, Jamaica, and entered into force on 16 November 1994 after Guyana became the 60th state to ratify it.

Today, over 168 UN member states plus the European Union are parties to UNCLOS. Notably, the United States has not ratified the treaty, though it observes UNCLOS as reflective of customary international law and its navy operates under its principles.

Key provisions and maritime zones 🔗

UNCLOS consists of 320 articles and nine annexes governing virtually all aspects of ocean use. One of its most significant achievements is the systematic division of ocean space into clearly defined maritime zones, each carrying specific rights and obligations. This zonal framework replaced centuries of ambiguity with measurable, internationally recognised boundaries.

Internal waters and the territorial sea 🔗

Under UNCLOS, a coastal state exercises full sovereignty over its internal waters – ports, rivers, and waters landward of the baseline. Beyond that, every state may claim a territorial sea extending up to 12 nautical miles from the baseline, within which it holds virtually complete authority. Foreign vessels, however, retain a right of innocent passage – they can transit the territorial sea as long as it is peaceful, continuous, and does not threaten the coastal state’s security.

Contiguous zone 🔗

Stretching up to 24 nautical miles from the baseline, the contiguous zone gives a coastal state limited enforcement powers. Specifically, it can take action in this zone to prevent or punish infringements of its customs, immigration, fiscal, and sanitary laws that occur within its territory or territorial sea.

Exclusive economic zone (EEZ) 🔗

The Exclusive Economic Zone extends up to 200 nautical miles from the baseline, and it is one of the most consequential innovations of UNCLOS. Within the EEZ, the coastal state holds sovereign rights over the exploration, exploitation, conservation, and management of all natural resources – both living and non-living – in the water column, the seabed, and its subsoil. This includes fish stocks, oil and gas deposits, and even energy generation from wind and tides.

At the same time, other states retain freedoms of navigation, overflight, and the laying of submarine cables within the EEZ. This balance between coastal-state economic rights and the international community’s navigational freedoms is central to how UNCLOS functions.

Continental shelf and the high seas 🔗

A coastal state’s rights over the continental shelf – the natural prolongation of its land territory beneath the ocean – can extend beyond 200 nautical miles if the state can demonstrate that the shelf meets certain geological criteria, potentially reaching up to 350 nautical miles. The Commission on the Limits of the Continental Shelf (CLCS), established by UNCLOS, reviews such claims.

Beyond all national zones lie the high seas, which remain open to all states under the principle of equal access. Activities there must be conducted for peaceful purposes. The seabed and ocean floor beyond national jurisdiction – known as “the Area” – and its mineral resources are designated as the common heritage of mankind, meaning no single nation can claim sovereignty over them.

Institutions created by UNCLOS 🔗

UNCLOS did not just set rules – it also created three key institutions to implement and enforce them:

International Tribunal for the Law of the Sea (ITLOS), based in Hamburg, Germany, adjudicates disputes arising from the interpretation or application of the convention. International Seabed Authority (ISA), headquartered in Kingston, Jamaica, regulates mineral exploration and mining activities in the Area. Commission on the Limits of the Continental Shelf (CLCS) reviews submissions from coastal states seeking to extend their continental shelf beyond 200 nautical miles. Together, these bodies provide the operational infrastructure that makes UNCLOS more than just a set of aspirational principles.

Environmental protection and biodiversity conservation 🔗

UNCLOS devotes an entire section – Part XII – to the protection and preservation of the marine environment. This was a landmark development. As the United Nations describes it, the general obligation for all states to protect and preserve the marine environment represented a radical shift from the fragmented approach of earlier treaties. It applies to all human activities and in all maritime zones.

Pollution prevention obligations 🔗

Part XII requires states to take measures to prevent, reduce, and control marine pollution from every source. It addresses vessel-source pollution, land-based pollution, pollution from dumping, seabed activities, and atmospheric sources. The convention works closely with the International Maritime Organization (IMO), which develops and adopts detailed technical regulations – such as the MARPOL Convention – to give these broad obligations practical, enforceable standards.

Biodiversity and ecosystem protection 🔗

UNCLOS also requires states to take necessary measures to protect rare or fragile ecosystems and the habitats of threatened, depleted, or endangered marine species. Within the EEZ, coastal states must ensure the sustainable management of fish stocks, setting allowable catches based on scientific evidence and cooperating with neighbouring states and regional fisheries organisations on shared stocks.

A major recent development is the BBNJ Agreement, commonly known as the High Seas Treaty, adopted in June 2023. This legally binding instrument supplements UNCLOS by addressing conservation of marine biodiversity in areas beyond national jurisdiction – covering marine protected areas, environmental impact assessments, marine genetic resources, and capacity building. As of mid-2025, 50 countries have ratified the agreement, with 60 ratifications needed for it to enter into force.

Climate change and the oceans 🔗

Although UNCLOS was drafted before climate change became a prominent global issue, its provisions have proven remarkably adaptable. In a landmark advisory opinion issued on 21 May 2024, ITLOS ruled that anthropogenic greenhouse gas emissions fall within UNCLOS’s definition of marine pollution. The tribunal affirmed that states have due diligence obligations to reduce emissions and protect the marine environment from climate impacts like ocean warming, sea-level rise, and acidification. This decision effectively expanded UNCLOS’s environmental reach into the climate governance space.

Dispute resolution mechanisms 🔗

One of UNCLOS’s most ambitious features is its compulsory dispute resolution system under Part XV. When states join the convention, they agree in advance to settle maritime disputes through binding procedures. This was a groundbreaking step that aimed to replace unilateral action with structured legal processes.

Available forums 🔗

States parties can choose from four forums for resolving disputes: the International Tribunal for the Law of the Sea (ITLOS), the International Court of Justice (ICJ), arbitration under Annex VII, or special arbitral tribunals under Annex VIII for technical matters. Before resorting to these binding mechanisms, states are expected to attempt peaceful resolution through negotiation, mediation, or conciliation.

Challenges in enforcement 🔗

In practice, enforcement remains UNCLOS’s most significant weakness. The South China Sea Arbitration of 2016 is the most prominent example: the Permanent Court of Arbitration ruled in favour of the Philippines, but China rejected the ruling and has faced no material consequences for non-compliance. UNCLOS contains no provisions for imposing sanctions, and its effectiveness ultimately depends on voluntary compliance by member states. When major powers refuse to abide by rulings, it raises questions about the system’s long-term credibility and whether smaller states will continue to trust the process.

Global impact and future challenges 🔗

UNCLOS has had an enormous positive impact on global maritime governance. It brought order to ocean boundaries, reduced maritime conflicts, protected navigational freedoms essential for international trade, and created a foundation for environmental stewardship of the seas. The convention governs activities over more than 70% of the Earth’s surface – a scope unmatched by any other international agreement.

Climate change and rising seas 🔗

Climate change poses existential challenges to the UNCLOS framework. Rising sea levels could redraw baselines from which maritime zones are measured, potentially shrinking or shifting EEZ boundaries for low-lying island states. Ocean warming and acidification threaten marine ecosystems that UNCLOS is meant to protect. While the 2024 ITLOS advisory opinion strengthened the legal link between UNCLOS and climate obligations, translating that into enforceable national action remains a work in progress.

Deep-sea mining 🔗

The prospect of mining polymetallic nodules and other minerals from the deep seabed has intensified debate over the ISA’s regulatory framework. Developing nations see deep-sea resources as an economic opportunity, while environmental groups warn of irreversible damage to poorly understood ecosystems. Striking the right balance between resource exploitation and environmental precaution will test the convention’s adaptability.

Geopolitical tensions 🔗

Maritime disputes in the South China Sea, the Arctic, and the East China Sea continue to test UNCLOS’s relevance. The convention’s inability to compel compliance from major powers like China, Russia, or the United States (which has not even ratified the treaty) highlights a structural limitation. Strengthening enforcement and ensuring that international law remains the foundation of maritime order is among the most pressing challenges facing the convention today.

Technological change 🔗

Advances in autonomous shipping, marine biotechnology, underwater drones, and offshore renewable energy are outpacing the legal frameworks that UNCLOS established over four decades ago. Supplementary agreements – like the BBNJ Agreement – represent one approach to keeping the convention current, but the pace of technological change demands ongoing legal evolution.

What do you think? Can a treaty written in 1982 continue to effectively govern the world’s oceans in an era of climate crisis and intensifying geopolitical competition? And should the enforceability of UNCLOS rulings be strengthened, or does the system of voluntary compliance remain the most realistic approach among sovereign nations?

References

1. https://maritimefairtrade.org/overview-of-the-united-nations-convention-on-the-law-of-the-sea-history-and-key-features/
2. https://www.un.org/en/global-issues/oceans-and-the-law-of-the-sea
3. https://www.noaa.gov/law-of-sea-convention
4. https://maritime-executive.com/article/Law-of-the-Sea-Mechanisms-Examining-UNCLOS-Maritime-Zones-2014-12-01
5. https://en.wikipedia.org/wiki/United_Nations_Convention_on_the_Law_of_the_Sea
6. https://www.tandfonline.com/doi/full/10.1080/00908320.2021.2011509
7. https://www.imo.org/en/mediacentre/secretarygeneral/pages/itlos.aspx
8. https://blogs.law.columbia.edu/climatechange/2024/05/24/unlocking-unclos-how-the-itlos-advisory-opinion-delivers-a-holistic-vision-of-climate-relevant-international-law/
9. https://rrdi.ro/2025/04/17/maritime-dispute-settlement-practice-unclos-mechanism-explained/
10. https://moderndiplomacy.eu/2024/07/17/international-law-and-the-challenges-in-implementing-unclos-south-china-sea-arbitration/