Around two thirds of the world’s ocean are considered ‘international waters’. They lie beyond the boundaries of any one country. 

The ‘high seas’ however are not lawless. Seafarers, ships, companies and countries are all subject to maritime law: a system of rules, international agreements and conventions that together govern activities on the high seas.

While these laws are meant to ensure that no single nation can lay claim to our ocean, they also come with a problem: if ‘no one’ owns the ocean, who’s responsible for caring for them?

A container ship at sunset
Photo by Ian Simmonds via Unsplash

One potential answer to that question came in 2023 with the passing of the UN High Seas Treaty – officially known as the International legally binding instrument under the United Nations Convention on the Law of the Sea on the conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction

It’s a long title for a long and potentially groundbreaking document. How did we get to this point, and how might the way the ocean is governed help safeguard the future of our planet?

Learn more with the National Maritime Museum.

Who owns the ocean?

No one owns the ocean. The seas and oceans are considered to be a ‘global commons’, which means that they belong to everyone and no one at the same time.

However, countries do have the right to claim ‘exclusive economic zones’ (EEZs) up to 200 nautical miles from their coastlines. Within these zones, countries have special rights to explore and exploit natural resources, such as fish, oil and gas.

Outside of these zones, both vessels and countries are subject to maritime law.


A map of the world showing Exclusive Economic Zones. The areas in dark blue are international waters.

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Map by B1mbo, CC BY-SA 3.0 CL, via Wikimedia Commons

What is maritime law?

Maritime law is a system of laws, conventions and regulations that govern activities on the seas and oceans. It covers a wide range of issues, from navigation, shipping, seafarer welfare and piracy to fishing, marine pollution and conservation. 

One of the principles of maritime law is the freedom of the high seas. This principle means that all countries have the right to use the oceans for navigation, fishing and other activities without interference from others. The ocean is free for all.

But there is a counter to this. The United Nations Convention on the Law of the Sea, adopted in 1982, recognises that the ocean is the ‘common heritage of humankind’, and that ‘No State shall claim or exercise sovereignty or sovereign rights over any part of the Area or its resources’.

While the ocean is free for all, it should not be a free for all, open to exploitation and abuse.

Major challenges around ratifying and enforcing the UN Convention on the Law of the Sea remain, and it has limited influence over what individual countries choose to do within their own exclusive economic zones.

However, recent developments show that maritime law can play an important role in ensuring the sustainability of the ocean and health of our planet.


"From oil to tin, diamonds to gravel, metals to fish, the resources of the sea are enormous. The reality of their exploitation grows day by day as technology opens new ways to tap those resources."

The United Nations Convention on the Law of the Sea – a historical perspective

What is the UN High Seas Treaty?

Efforts to increase international cooperation around the protection of the ocean have been ongoing for many years, with the United Nations (UN) at the forefront.

One of the most significant recent developments is the so-called UN High Seas Treaty, an agreement reached in March 2023 following years of negotiations. If ratified, the treaty could lead to better protection for marine life and more sustainable management of the ocean’s resources.

This treaty allows for the creation of a network of marine protected areas, designed to ‘protect, preserve, restore and maintain biodiversity and ecosystems’.

This could aid the campaign to protect 30 per cent of the ocean by 2030, one of the key targets of the UN’s 17 Sustainable Development Goals for 2030.

The treaty also requires countries to conduct Environmental Impact Assessments (EIAs) on planned marine activities such as deep sea mining before they are authorised. This is designed to lead to better understanding of human impacts on the ocean, and challenge actions ‘that may cause substantial pollution of or significant and harmful changes to the marine environment’.

The High Seas Treaty has been called a ‘breakthrough’ for international conservation efforts and marine diversity. But there is still work to be done: countries must first legally adopt the agreement and then work together to implement the treaty’s requirements.


"We are delighted to hear that the UN High Seas Treaty has finally become a reality.

"A healthy Ocean is vital for the survival of all living things, and this is the message we continue to deliver through our work at Ocean Generation. Protecting 30% by 2030 must, however, be seen as a minimum requirement.

"We view this agreement as a starting point. The Ocean is our ally in the fight against climate change and we must stop underestimating its role in our survival. The sooner this treaty is ratified by all countries, the better chance we have of a safe and healthy future for the generations that will follow us."

Jo Ruxton MBE, Founder of Ocean Generation

Our Ocean, Our Planet

Explore ocean issues, the climate crisis and our changing relationship with the sea online with the National Maritime Museum

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