Maritime Boundaries and the Evolving Law of the Sea

In recent years, maritime boundary disputes have been commonplace in the international legal arena. This is because most countries today are becoming more and more interested in and concerned about maritime boundaries for the exploration and exploitation of both mineral and food resources. Among the most controversial maritime boundary disputes in the world over the past couple of years is the West Philippine Sea conflict. This dispute has been ongoing for decades and is ultimately a result of years of territorial conflict over the “Spratly Islands,” a group of around 7,500 islands and reefs claimed by several countries to be their own.

However, maritime disputes like the West Philippine Sea conflict are a global menace because they disrupt the political harmony in international relations. As such, the importance of rapidly settling these maritime boundary disputes cannot be stressed enough, as it is a key to the peaceful coexistence of States in the international realm. To this end, the support and guidance of reputable international organisations, such as the United Nations, are necessary. These organisations assist in formulating policies and procedures for an effective delimitation of maritime boundaries in accordance with the so-called “Law of the Sea.”

What is the Law of the Sea?

The term “Law of the Sea” basically refers to a branch of international law that deals with or is concerned about public order at sea. A majority of this law has been codified in the United Nations Convention on the Law of the Sea (UNCLOS), which is often regarded as the “constitution for the oceans.” Signed on the 10th of December 1982, UNCLOS reflects an attempt by numerous States to codify international law with respect to ocean resources, sea lanes, and territorial waters. It came into effect only in 1994, following its ratification by 60 States. By the early 21st century, over 150 States had already ratified UNCLOS.

The Different Maritime Zones Under UNCLOS

Defining maritime zones is one of the biggest contributions of UNCLOS to international law. Maritime zones in international law are areas of sea or ocean which are subject to national or international authority. These zones essentially serve as maritime borders that are delimited as parts of the sea surface, seabed, and water column, the subdivision of which is based on the grounds of political jurisdiction in relation to the ownership and use of marine resources. Under UNCLOS, there are mainly five recognised maritime zones in international law, namely internal waters, territorial sea, contiguous zone, exclusive economic zone, and the high seas.

1. Internal Waters

The term “internal waters” refers to those waters found on the baseline’s landward side from which the territorial sea’s breadth is being measured. Over its internal waters, every coastal State has complete sovereignty as if it forms part of its land territory. As such, the coast State has the authority to exclude foreign flag ships from its internal waters, except when the right of entry of ships in distress is invoked. In internal waters, the right of innocent passage, which refers to the right of foreign ships to navigate the sea of another State freely without performing activities that are prejudicial to the latter’s interests, is not applicable. 

2. Territorial Sea

Every coastal State can claim a territorial sea, which is basically a belt of coastal waters that extend up to 12 nautical miles from the baseline. A coastal State likewise exercises sovereignty over its territorial sea, the subsoil and seabed underneath it, and the airspace above it. Unlike in internal waters, international law authorises foreign flag ships to freely transit the territorial sea of another State in the exercise of the right of innocent passage. However, the exercise of this right is subject to the laws and regulations that are adopted by the coastal State in accordance with UNCLOS and other rules of international law in respect of such passage.

3. Contiguous Zone 

Every coastal State is also empowered to claim a contiguous zone, which is beyond and adjacent to its territorial sea and extends seaward up to 24 nautical miles from the baseline. Within this maritime border, a coastal State can exercise the kind of control necessary to avert the infringement of its fiscal, immigration, customs, or sanitary laws and regulations within its territorial sea or land territory. In line with this power, the coastal State may also punish any entity that commits such infringement. In addition, to control trafficking in historical and archaeological objects found at sea, every coastal State has in its favour the presumption that the removal of such objects from the seabed of its contiguous zone without its consent is illegal. 

4. Exclusive Economic Zone

Exclusive economic zones are another maritime boundary defined under the UNCLOS. Basically, an exclusive economic zone is an area of sea or ocean that generally extends seaward up to 200 nautical miles beyond the territorial sea of a coastal State. Within the exclusive economic zone, a coastal State has the following:

  • Sovereign rights to conserve, explore, exploit, and manage the natural resources, whether living or non-living, of the subsoil, seabed, and superjacent waters with respect to other activities for the economic exploration and exploitation of the zone, such as the generation of energy from the water, winds, and currents.
  • Jurisdiction with regards to the establishment and utilisation of artificial islands, structures, and installations, marine scientific research, and the preservation and protection of the marine environment.
  • Other rights and obligations as may be provided for under international law. 

5. The High Seas 

Under international law, the high seas are defined as all parts of the sea or ocean, which are not included in the internal waters, the territorial sea, or the exclusive economic zone of any State. In other words, the high seas and all the resources found therein are not directly regulated or owned by any country. Not being owned by any State, UNCLOS mandates that the high seas shall be reserved for peaceful purposes only. Any State may not legally purport to subject any part of the high seas to its sovereignty. In line with this, all States, whether land-locked or coastal, have the right to sail ships on the high seas.

Is UNCLOS Legally Binding?

A common question that many individuals and organisations have when it comes to UNCLOS is whether it has the power to enforce its rules and decisions, specifically with regard to the settlement of maritime disputes. The simple answer to this question is yes – the UNCLOS verdicts are deemed legally binding on its member States pursuant to the principle of “pacta sunt servanda,” which is the oldest generally accepted principle of international law that literally means “agreements must be kept.”

At present, UNCLOS has already been ratified by 168 parties, which comprise 167 States and the European Union (EU). 14 UN member States have additionally signed the convention but have not yet ratified the same. Because of opposition from Republicans in the Senate, the United States has not been able to ratify the UNCLOS. Nonetheless, it now recognises the convention as a codification of customary international law.

In Asia, most countries are members of UNCLOS, including China and the Philippines. It is for this reason that both States, specifically China, are being pressured to abide by the 2016 Arbitral Tribunal ruling, which essentially determined the major elements of China’s claim over the West Philippine Sea – including its recent land reclamation activities, other activities in Philippine waters, and the nine-dash line – to be unlawful. However, to this day, China still refuses to honour such a verdict in violation of UNCLOS’ decision and of international law in general.


The creation of UNCLOS has ultimately changed the way marine resources and territories are regulated and maritime disputes are settled. Although arguably not a perfect law, UNCLOS deserves to be lauded for laying down essential laws and rules whose global acceptance is believed to have greatly reduced the frequency, number, and potential for inter-state disputes that would otherwise have taken place. Among the biggest contributions of UNCLOS to international law is the definition and delimitation of maritime zones, which have greatly helped States determine their maritime boundaries, rights, and obligations.

About Maritime Fairtrade

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