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Max Planck Encyclopedia of Public International Law [MPEPIL]

Gibraltar, Strait of

Donald R Rothwell

From: Oxford Public International Law (http://opil.ouplaw.com). (c) Oxford University Press, 2023. All Rights Reserved.date: 19 June 2024

Straits — UNCLOS (UN Convention on the Law of the Sea) — Innocent passage — Marine environment, protection

Published under the auspices of the Max Planck Institute for Comparative Public Law and International Law under the direction of Professor Anne Peters (2021–) and Professor Rüdiger Wolfrum (2004–2020). 

A.  History and Geography

The Strait of Gibraltar (‘the Strait’) is a body of water at the western extremity of the Mediterranean Sea which connects the Mediterranean with the Atlantic Ocean. It is one of the most significant global sea lanes because it provides a means of seaborne transit for shipping between the Atlantic and Mediterranean, and via the Suez Canal into the Indian Ocean and beyond. Because of its strategic location, and the access that it has granted to the States which fringe the Mediterranean in both Southern Europe and Northern Africa, the Strait has longstanding historic and strategic significance.

The Strait lies between the southern most tip of Spain and the northern tip of Morocco. At the north eastern edge of the Strait is the territory of Gibraltar, which is governed by the United Kingdom. Whilst Britain has exercised effective control over Gibraltar since 1713, its status has been contested by Spain for many centuries. The Bay of Gibraltar, which separates Gibraltar from the Spanish town of Algeciras, is an indentation along the southern Spanish coastline which fronts directly onto the Strait. The small Spanish enclave of Ceuta is at the south eastern extremity of the Strait on the African coast (Ceuta and Melilla). In the 20th century, up until 1956, France asserted control over part of Morocco including that area which fronted the Strait. The States which therefore currently have direct interests over the Strait, and which assert maritime claims over the waters of the Strait, are Morocco, Spain, and the United Kingdom.

Between its entry and exit points, the Strait is 36 miles long and less than 8 miles wide at the point between Point Marroque (Spain) and Point Cires (Morocco). The western extremity of the Strait between Cape Trafalgar (Spain) and Cape Spartel (Morocco) is 27 miles long. The eastern extremity of the Strait between Europa Point (Gibraltar) and Ceuta is 14 miles long.

B.  International Navigation in the Strait of Gibraltar

In 2006 it was estimated that east–west traffic through the Strait totalled 65,000 vessels while cross-strait north–south traffic was 30,000 vessels. The cross-strait traffic included more than 5 million passengers, 1.3 million vehicles and 190,000 trucks. The significance of the ‘sea bridge’ between Southern Europe and North Africa is such that consideration is being given to the building of an undersea rail tunnel across the Strait, which would ease the movement of goods and persons, thereby reducing cross-strait sea traffic, which in turn would reduce some of the navigational congestion in the Strait.

There are a number of significant ports along the Strait, including the Port of Algeciras, the Port of Gibraltar, and the Port of Tangier. The capacity of these ports is increasing with new terminals having opened or being planned for the Spanish and Moroccan ports and coast. In addition, Morocco announced in 2008 its intention to build its first Mediterranean naval base between Ceuta and Tangier. Significant bunkering operations are conducted in some of these ports, which carries an associated risk of fuel spillage (see also Environmental Accidents).

Until the opening of the Suez Canal in 1869, the Strait of Gibraltar was the only means of oceanic access to and from the Mediterranean Sea. The longstanding strategic importance of the Strait has been well recognized throughout history, and this is reflected in the contests that have taken place between major maritime powers over control of the Strait. The closure of the Suez Canal between 1968–1975 highlighted the importance of the Strait as the only means of seaborne access to the Mediterranean Sea. In more recent decades the role of the Strait in combination with the Suez Canal as the primary sea routes for trade between Europe and the growing markets of East and South Asia, and as a route for tanker traffic carrying Middle East oil for European markets, has only served to reconfirm the 21st century significance of the Strait.

C.  Historical Constraints upon Navigation

Due to the strategic significance of the Strait, navigational rights have been closely controlled throughout history (Navigation, Freedom of). Spain gained control of territory on either side of the Strait in 1610, and notwithstanding the subsequent British control acquired over Gibraltar by the 1713 Treaty of Peace and Friendship between Great Britain and Spain (‘Treaty of Utrecht’), it was Spain which exercised control over the Strait up until the late 19th century. Whilst rarely seeking to close the Strait completely, Spain did require merchant vessels (Merchant Ships) to hoist their flags when passing through the Strait in order to identify themselves (see also Flag of Ships). This practice continued until as late as 1864 when the British vessel Mermaid was subject to cannon fire as a result of a failure to hoist its ensign. Spain abolished its practice of requiring ship identification by way of the Declaration between Great Britain and Spain for the Abolition of the Practice of Firing on Merchant Vessels from British and Spanish Forts in the Straits of Gibraltar of 1865. However, passage through the Strait remained a sensitive issue, and in the 1904 Declaration between France and Great Britain Respecting Egypt and Morocco concluded at a time when France had control of the North African coast it was provided that

In order to secure the free passage of the Straits of Gibraltar, the two Governments agree not to permit the erection of any fortifications or strategic works on that portion of the coast of Morocco comprised between, but not including, Melilla and the heights which command the right bank of the River Sebou. (Art. VII Declaration between France and Great Britain Respecting Egypt and Morocco)

D.  The Law of the Sea and International Navigation

The contemporary law of the sea has had a significant impact upon navigation through the Strait of Gibraltar. As the law of the sea has progressively recognized the right of coastal States to assert territorial sea claims, straits of a certain breadth have been converted from bodies of water through which high seas navigation could be enjoyed to areas which fell within a territorial sea regime. Initially, because the Strait of Gibraltar was greater than 6 nautical miles at its narrowest point, there remained a high seas corridor through which ships could pass under the customary international law regime of a 3 nautical mile territorial sea. However, once the breadth of the territorial sea was extended to 12 nautical miles under the 1982 United Nations Convention on the Law of the Sea ([signed 10 December 1982, entered into force 16 November 1994] 1833 UNTS 396; ‘UN Convention on the Law of the Sea’), straits such as Gibraltar were prone to overlapping territorial sea claims by the adjoining coastal States, which potentially had a capacity to place significant constraints upon the freedom of navigation. In the case of the Strait of Gibraltar, this was a particular issue because of its strategic significance, and due to the potential for three States to assert overlapping territorial sea claims over the waters of the Strait.

1.  Status of the Strait of Gibraltar under International Law

Part III UN Convention on the Law of the Sea provides a distinctive regime for straits used for international navigation (Straits, International). Whilst Part III UN Convention on the Law of the Sea addresses the circumstances of a number of different types of straits, the Strait of Gibraltar falls within the principal category of straits which were the main focus of attention during the negotiations at the Third United Nations Conference on the Law of the Sea (Conferences on the Law of the Sea). As the Strait of Gibraltar is a strait through which no high seas corridor exists, and which is used by international navigation for passage between one part of the high seas or the exclusive economic zones (Exclusive Economic Zone; ‘EEZ’) in the Atlantic Ocean and another part of the high seas or the EEZ in the Mediterranean Sea, it is a strait through which the right of transit passage applies.

10  An alternate position with respect to the application of Part III UN Convention on the Law of the Sea is that the Strait of Gibraltar is governed by a ‘long-standing international convention’ with the result that under Art. 35 (c) UN Convention on the Law of the Sea, the transit passage regime does not apply. The basis for this position, asserted by Italy and the USSR during the Third United Nations Conference on the Law of the Sea, rests with an interpretation of the 1904 Declaration between France and Great Britain Respecting Egypt and Morocco, and the subsequent 1912 Convention between France and Spain respecting Relations in Morocco under which the freedom of navigation through the Strait was guaranteed. Both Spain and Morocco rejected this interpretation during Conference deliberations and at best it remains a minority position and does not reflect the contemporary right of transit passage through the Strait.

11  Spain has been careful to ensure that its rights under the Treaty of Utrecht are not prejudiced by its ratification of the UN Convention on the Law of the Sea, and upon signing and ratifying the Convention lodged a declaration to the effect that ‘this act cannot be interpreted as recognition of any rights or situations relating to the maritime spaces of Gibraltar which are not included in article 10 of the Treaty of Utrecht’ (United Nations Division for Ocean Affairs and the Law of the Sea (ed), The Law of the Sea: Declarations and Statements with Respect to the United Nations Convention on the Law of the Sea and to the Agreement relating to the Implementation of Part XI of the United Nations Convention on the Law of the Sea of 10 December 1982 [United Nations New York 1997] 16).

2.  Transit Passage Regime

12  Importantly for the Strait of Gibraltar, it, along with a number of other strategically important straits throughout the world, was the subject of special attention during the negotiations at the Third United Nations Conference on the Law of the Sea resulting in recognition being granted to a new regime of transit passage which applied in certain international straits. The right of transit passage permits shipping a right of navigation for the purposes of ‘continuous and expeditious transit of the strait’ (Art. 38 (2) UN Convention on the Law of the Sea) and thereby allows for ongoing navigation rights of access and egress to the Mediterranean Sea. Navigational rights through the Strait of Gibraltar are therefore in the first instance governed by the transit passage regime of the UN Convention on the Law of the Sea, supplemented by additional international instruments dealing with matters such as safety of shipping (see also Maritime Safety Regulations), and protection of the marine environment (Marine Environment, International Protection), and in addition applicable coastal State laws and regulations adopted by the strait States in conformity with international law.

3.  Maritime Zones within the Strait

13  The relevant maritime zones claimed by the strait States include a 12 nautical mile territorial sea, a 24 nautical mile contiguous zone, and a 200 nautical mile EEZ, though Spain’s claim only extends to the Atlantic Ocean. In the case of Gibraltar, the United Kingdom only claims a 3 nautical mile territorial sea. The consequence of this is that on the western approach to the Strait ships pass through the EEZs of either Spain or Morocco, through which they enjoy the freedom of navigation, until such time as they enter either State’s territorial sea at which point the transit passage regime commences. A right of transit passage is then enjoyed as a ship passes through the Strait, including through the territorial sea generated offshore to Gibraltar. Once a ship exits the Strait and passes into the Mediterranean Sea proper, the vessel will in most instances enter EEZ or high seas areas within which the freedom of navigation can be exercised.

E.  Safety of Navigation in the Strait of Gibraltar

14  Consistent with the regime of transit passage under the law of the sea, including other international conventions such as the 1972 Convention on the International Regulations for Preventing Collisions at Sea ([signed 20 October 1972, entered into force 15 July 1977] 1050 UNTS 17; ‘COLREGS Convention’; Collisions at Sea) and the International Convention for the Safety of Life at Sea ([signed 1 November 1974, entered into force 25 May 1980] 1184 UNTS 2; ‘SOLAS Convention’), the International Maritime Organization (IMO) has proclaimed a traffic separation scheme in order to ensure the safe passage of shipping through the Strait. The scheme, which is given the force of law under the SOLAS Convention, is subject to ongoing review and adjustment to reflect changes in traffic levels and direction. To further enhance the safety of shipping as it passes through the Strait, in 1997 a mandatory ship reporting system was put in place in the Strait of Gibraltar. All ships passing through the Strait are therefore required to comply with the provisions of the ship reporting system, which has been developed in accordance with IMO guidelines and has its legal basis in the SOLAS Convention.

F.  Overflight in the Strait of Gibraltar

15  The international regime of straits as provided for under the UN Convention on the Law of the Sea also provides for a right of overflight in international straits. Overflight can therefore be exercised through the Strait of Gibraltar consistent with the UN Convention on the Law of the Sea, which requires that civil aircraft observe internationally agreed rules of the International Civil Aviation Organization (ICAO) (see also Air Law). This is an important right as it means that civil aircraft do not need to overfly land territory to access the Mediterranean Sea at its western extremity, and, given the longstanding dispute which has existed between Spain and the United Kingdom with respect to Gibraltar, has meant that civil aircraft can approach Gibraltar airport without the need to overfly Spain.

G.  Marine Environmental Protection in the Strait of Gibraltar

16  Due to the volume of navigation through the Strait of Gibraltar there are risks associated with collisions resulting in significant marine pollution, or the spillage of oil and other substances by ships engaged in passage (see also Marine Pollution from Ships, Prevention of and Responses to). These issues are partly addressed through IMO conventions such as the COLREGS Convention and SOLAS Convention, but are also covered by specific marine pollution conventions. The Mediterranean Sea has long been recognized as a ‘special area’ under the Convention for the Prevention of Pollution from Ships ([signed 2 November 1973, entered into force 2 October 1983] 1340 UNTS 184) and the Protocol of 1978 Relating to the International Convention for the Prevention of Pollution from Ships (with Annexes, Final Act and International Convention of 1973) ([signed 17 February 1978, entered into force 2 October 1983] 1340 UNTS 61; ‘MARPOL 73/78’). ‘Special areas’ are those bodies of water which, due to technical reasons relating to their oceanographical and ecological conditions when combined with their volume of sea traffic, have had special mandatory methods adopted for the prevention of certain type of marine pollution. The Mediterranean Sea has been a special area under Annex I MARPOL 73/78 since 1983 with the effect that significant constraints are placed upon the discharge by ships of oil. The Mediterranean is also subject to ‘special area’ designation under Annex V MARPOL 73/78 dealing with limitations on the disposal by ships of ‘garbage’, which was adopted in 1988 but as of 2008 had yet to enter into force. Ships entering the Strait of Gibraltar from the Atlantic Ocean therefore become subject to these enhanced Mediterranean Sea marine pollution provisions as they transit the strait.

17  In addition to the relevant international marine pollution conventions and regimes, the waters of the Strait of Gibraltar have increasingly become subject to more stringent marine environmental protection measures adopted by the literal States. Following significant maritime casualties such as the Agean Sea (1992) and the Prestige (2002), Spain announced that as from 1 January 2003 single-hull tankers flying any flag and carrying heavy fuel oil, coal tar, or heavy crude oil would be prohibited from entering Spanish ports, terminals, or anchorage areas. Whilst this Spanish decree could not limit transit passage through the Strait of Gibraltar due to freedoms associated with transit passage under the law of the sea, the practical effect of this provision was to impact upon a considerable volume of shipping passing through the Strait because of their need to stop at Spanish ports for either bunkering services or to offload cargo.

H.  Military Uses of the Strait of Gibraltar

18  In recent years, as the strategic importance of the Strait of Gibraltar has grown, there has been an increased military usage of the Strait. Joint exercises are conducted from time to time by Spanish and Moroccan armed forces, which may also be conducted in conjunction with North Atlantic Treaty Organization (NATO) forces. However, the law of the sea makes clear that it is not possible to suspend transit passage through the Strait even in the event of military exercises taking place. This is to be contrasted with provisions dealing with innocent passage in the territorial sea, which can on an occasional basis be subject to temporary suspension when military exercises are taking place within those waters (see also Naval Demonstration and Manoeuvres).

19  Following the terrorist attacks upon Washington and New York in 2001 heightened security measures were put in place in some strategic international sea lanes. In 2003, NATO announced that Alliance naval forces would escort Allied commercial and civilian naval vessels through the Strait of Gibraltar as a measure to protect shipping from terrorist attacks (see also Terrorism).

I.  Significance of the Strait of Gibraltar to International Law

20  The Strait of Gibraltar continues to be of considerable economic, historic, legal, and strategic significance, and this may further develop in future years as links between North Africa and Southern Europe expand. The Strait is an area in which there is considerable legal history with respect to not only its status, but also the surrounding lands and the practice of maritime law within its waters. In contemporary times the Strait is an example of the implementation of the transit passage regime of the UN Convention on the Law of the Sea, and also illustrates the complex interaction of that regime with other applicable conventions dealing with marine pollution and more generally maritime law.

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