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Law of the sea

by  Bill Mansfield

The 1982 United Nations Convention on the Law of the Sea has been called one of the UN’s greatest achievements. It provided international checks and balances on the use of the oceans. For coastal nations such as New Zealand, the benefits were huge – control of fisheries and other resources inside exclusive economic zones.

Control of the oceans

The freedom of the seas

As soon as ocean-going ships were developed, the seas became a battleground, or a route to a battleground. Countries also began to claim ownership or control of oceans nearby. It became clear that if the seas could be claimed in the same way as land, there was likely to be increased competition and conflict between countries.

As free as the breeze

In 1609 young Dutch legal thinker Hugo Grotius wrote the controversial Mare liberum, about the law of the sea. He proposed that ‘the sea, since it is as incapable of being seized as the air, cannot be attached to the possession of any particular nation’, and that ‘every nation is free to travel to every other nation, and to trade with it’. Mare liberum was later seen as the inspiration for the concept of ‘freedom of the seas’.

To reduce that risk, the legal concept of ‘freedom of the seas’ was developed in the early 17th century. The underlying philosophy was that the oceans were an infinite resource, and that anyone could exploit them, or use them for travel and transport. This became generally accepted for waters beyond a ‘territorial’ sea which stretched about 3 nautical miles from land.

The threat of conflict

International law based on freedom of the seas remained largely unchanged and unchallenged until the middle of the 20th century. By then, many states with sea coasts realised that the relatively few countries with large naval, merchant or fishing fleets could engage in threatening or dangerous activities. They could also exploit fisheries or mineral resources such as oil at great distances from their own shores and close to the coasts of other countries.

A number of these coastal states began to claim ownership of, or exclusive fishing rights over, much wider territorial seas. Other states with little or no sea coast also sought a share in the resources. As a result, the risk of widespread conflict over control of the seas and their resources re-emerged.

New Zealand’s changing perspective

Of all the livable places of any real size, New Zealand is one of the most isolated. It was also the last to be discovered. This isolation has had a profound effect on its attitude towards international management of the oceans, and their use as communication and transport highways.

In 1958 and 1960 the United Nations made largely unsuccessful attempts to address an increasingly unstable situation. New Zealand supported the maritime powers, notably the United States and Britain, in their efforts to preserve traditional open seas freedoms and to restrict the claims of coastal states. The country was conscious of its isolation and dependence on those freedoms for trade with its distant markets, especially Britain. It was also aware that as a member of Western defence alliances, its security relied on the wide-ranging deployment of naval forces.

But by 1974, when the Third United Nations Conference on the Law of the Sea was held, New Zealand had passed laws to protect its coastal fisheries for a distance of 12 nautical miles from shore. A new view had emerged: New Zealand’s isolation could be turned to its advantage. The country could control more resources if the concept of an exclusive economic zone for coastal states gained international acceptance.

United Nations convention, 1982

The 1982 United Nations Convention on the Law of the Sea (UNCLOS) was the result of the conference held in 1974. The Convention is one of the most significant but least recognised accomplishments of the United Nations.

A peaceful revolution

The agreement, while revolutionary, was achieved by negotiation. It was founded on the idea that all issues relating to the oceans are closely linked and must be dealt with as a whole.

Today it is one of relatively few international agreements that all countries comply with in practice – even those few that are not yet formally bound to it.

The convention’s provisions

UNCLOS strikes a delicate balance between competing interests in the use of the oceans. Among many provisions, it:

  • sets the maximum breadth of the territorial sea at 12 nautical miles, with a right of peaceful passage for foreign ships
  • ensures unhindered transit passage for vessels and aircraft through and over international straits and through waters with many islands
  • provides coastal states with exclusive rights over all resources in an exclusive economic zone out to 200 nautical miles, while preserving pre-existing navigational and other rights within these areas
  • affirms coastal state rights over continental shelves extending beyond 200 nautical miles, subject to certain limitations
  • guarantees access to and from the sea for landlocked states
  • establishes a regime for the development of the mineral resources of the deep seabed beyond national jurisdiction, and declares that area to be the common heritage of mankind
  • sets rules for the conduct of marine scientific research
  • imposes duties regarding the conservation and management of high-seas fisheries and the protection of the marine environment
  • establishes procedures for the compulsory settlement of disputes.

New Zealand’s role in negotiations

New Zealand’s active participation included:

  • supporting the freedom of navigation essential for getting its products to distant markets
  • joining the effort to strengthen the rules allowing foreign vessels to pass through territorial seas and international straits.

But New Zealand’s main focus was to secure for coastal states the right to control the resources in a broad area near their coasts. In particular, New Zealand sought to apply this right to small islands as well as larger land masses. In this latter objective, initially opposed by many states, New Zealand shared an interest with many of the island states of the South Pacific, and worked closely with them.

A sea change

In 1994, UN Secretary-General Boutros Boutros-Ghali described the 1982 convention as among the greatest achievements of the 20th century. Turning the age-old dream of a comprehensive law of the ocean into reality was, he claimed, one of the UN’s most enduring legacies.

Sustainable management

New Zealand, the Pacific Island countries, and many other coastal states built their case for control over fisheries resources out to 200 nautical miles on the principle of sustainable management. They argued that, unlike states that fished in distant waters, they had an ongoing interest in maintaining their coastal fisheries. They also pushed for all countries to take responsibility for conserving and managing fisheries in the open seas.

The benefits for New Zealand

The UN Convention on the Law of the Sea was adopted in 1982, after nearly 10 years of negotiation. Its terms could scarcely have been better from the standpoint of New Zealand and its Pacific Island neighbours.

The Exclusive Economic Zone

Islands were entitled to the same maritime spaces as larger land areas. In New Zealand’s case, the convention justified using the small islands to the north, east and south of the three main islands as base points for an Exclusive Economic Zone (EEZ). As a result, New Zealand’s EEZ covers 4 million square kilometres – the fourth largest in the world.

Pacific Islands

Pacific Island countries were entitled to establish EEZs (in many cases using very small islands as base points) covering vast areas of the Pacific Ocean. A particular benefit was that they could license access to the valuable tuna that migrate through these waters.

New Zealand, supported by the independent Pacific states, also obtained the right for the Cook Islands and Niue (which are self-governing, but in free association with New Zealand) to sign the convention in their own right. This enabled them to accept directly the convention’s benefits and obligations.

Other benefits

With rights over the resources of its continental shelf even beyond 200 nautical miles, New Zealand claimed a further 1.9 million square kilometres of seabed resources.

The convention clarified and strengthened the rules regarding the rights of foreign vessels to pass through territorial seas and international straits. It also preserved navigational freedoms in EEZs and on the open seas beyond those zones. These measures safeguarded New Zealand’s position as a trading nation. It can send and receive goods by ships that, for parts of their journey, must travel close to the coasts of other countries.

An issue of sovereignty

The Exclusive Economic Zone created significant economic opportunities. Although a coastal state does not have the same sovereignty over the zone as it does over the territorial sea, it does have the right to exploit its resources.


The major economic gains have been in fisheries. In the 1960s New Zealand’s small coastal fishing industry aimed simply to keep foreign vessels from fishing any closer than 12 nautical miles from the coastline. Before the EEZ was established, the value of fish exports peaked at about $50 million.

In the 2000s, fish exports exceeded $1 billion annually. New Zealand fishing vessels fish not only the entire allowable catch within the EEZ, but also the open seas from the Antarctic to the North Atlantic. There is ongoing debate in New Zealand as to the effectiveness of fisheries management within the EEZ. Nevertheless, without the right to establish and manage that zone, fish stocks would have been seriously depleted by unrestricted foreign fishing.

Oil and gas

So far the exploitable offshore oil and gas discoveries around New Zealand have been relatively close to the coast. The potential for such discoveries on the continental shelf beyond 200 nautical miles is thought to be low. But the continental shelf rights mean that New Zealand will benefit from any new mineral or biological resources discovered in this very broad area. New Zealand also has the right to ensure that any exploration and exploitation is carried out with careful regard for the marine environment.

New Zealand completed the process of defining the outer limits of its continental shelf in 2006, and submitted these to the Commission on the Limits of the Continental Shelf for endorsement, which it received in 2008. It also had to delimit its boundaries with neighbouring states.

Protecting the oceans

Oceans at risk

Although the 1982 United Nations Convention on the Law of the Sea established new laws, it could not guarantee that they would be managed wisely. It envisaged that coastal states would develop rules governing their marine environments, including fisheries in their exclusive economic zones (EEZs). Also needed were more specific international and regional rules to ensure the sustainable management of open-seas fisheries, and to set safety and environmental standards for international shipping.

Action programmes, additional rules, and new management bodies have achieved much. But the state of the world’s oceans continues to deteriorate. The three greatest threats remain:

  • pollution from land-based sources
  • overfishing
  • destruction of marine habitats.

The international community faces many other complex problems, including criminal activities such as terrorism, piracy, migrant smuggling and illicit traffic in drugs, arms and other goods. There is also the major issue of rising sea level caused by global warming.

New Zealand’s response

Joining in the effort to protect the world’s oceans, New Zealand has:

  • participated in global efforts to reduce pollution from land sources, which accounts for 80% of all ocean pollution.
  • sought to reduce the pollution that enters its coastal waters from the land.
  • drawn attention to the fact that over 70% of the world’s fisheries are being fished at or above sustainable levels.
  • promoted international action to eliminate destructive fishing practices such as drift netting.
  • played a prominent part in establishing a forum within the United Nations where issues can be discussed informally, drawing on a range of expertise.

Overfishing and illegal fishing

New Zealand is particularly concerned to manage its fisheries and protect the marine environment both within its EEZ and in surrounding waters, including the Southern Ocean.

Cleaning up our own act

While critical of other countries for destructive fishing, New Zealand is not above reproach. Some of its own vessels practise bottom trawling. This has an extremely detrimental effect on the sea-floor environment, and has drawn international criticism.

The massive over-capacity of the world fishing fleet is a major concern for New Zealand. The world fishing fleet already has at least double the capacity needed for sustainable catch levels. It discards 25% of its catch, and would run at a loss but for government subsidies.

The failure of many states to stop their vessels engaging in illegal, unreported and unregulated fishing on the high seas or in other EEZs is another significant problem.

Supporting the UN convention

New Zealand has a vested interest in supporting the UN Convention on the Law of the Sea in its present form. It seems most unlikely that any renegotiation would produce such a favourable result. Therefore, New Zealand can be expected to play an active role in the development of new measures and agreements to deal with current problems and any others that emerge. The convention provides the stable legal framework against which such solutions can be developed.

Hononga, rauemi nō waho

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How to cite this page: Bill Mansfield, 'Law of the sea', Te Ara - the Encyclopedia of New Zealand, (accessed 10 August 2022)

He kōrero nā Bill Mansfield, i tāngia i te 12 Jun 2006