Malacca, Singapore, Sunda, Lombok, and the Northeast, Northwest, and Windward Passages fall into this category. However, it is use for international navigation, not importance, that is the basic legal criterion, as described below.
Archipelagic sea lanes passage replaces transit passage as the relevant regime that applies to straits within archipelagic waters and the adjacent territorial sea, where archipelagic waters affecting such straits are established in accordance with Part IV of the Convention. This would be the situation, for example, in the Sunda and Lombok straits were Indonesia to designate archipelagic sea lanes. Transit passage applies to routes through islands groups to which the provisions regarding archipelagic waters do not apply.
Non-suspendable innocent passage applies to straits connecting a part of the high seas/EEZ and the territorial sea of a foreign State (article 45(1)(b)), and to straits connecting one part of the high seas/EEZ and another part of the high seas/EEZ where the strait is formed by an island of a State bordering the strait and its mainland, if there exists seaward of the island a route through the high seas/EEZ of similar convenience with regard to navigation and hydrographic characteristics (article 38(1)).
In addition, the Convention does not alter the legal regime in straits regulated by long-standing international conventions in force specifically relating to such straits. This provision refers to the Turkish Straits (the Bosporus and Dardanelles, connecting the Black Sea and the Aegean Sea via the Sea of Marmara) and the Strait of Magellan.
Transit Passage. Part III of the Convention protects long-standing navigation and overflight rights in international straits through the concept of transit passage. This is the regime governing the right of free navigation and overflight for ships and aircraft in transit in, over, and under straits used for international navigation. Recognition of such a right was a fundamental requirement for a successful Convention. With the extension by coastal States of their territorial seas to 12 miles, over 100 straits, which previously had high seas corridors, became overlapped by such territorial seas. Without provision for transit passage, navigation and overflight rights in those straits would have been compromised. Read together, articles 38(2) and 39(1)(c) define transit passage as the exercise of the freedom of navigation and overflight solely for the purpose of continuous and expeditious transit in the normal modes of operation utilized by ships and aircraft for such passage.
For example, submarines may transit submerged and military aircraft may overfly in combat formation and with normal equipment operation; surface warships may transit in a manner necessary for their security, including formation steaming and the launching and recovery of aircraft, where consistent with sound navigational practices.
Article 38(3) provides that any activity which is not an exercise of the right of transit passage remains subject to the other applicable provisions of the Convention.
Under article 44, a State bordering an international strait may not suspend transit passage through international straits for any purpose, including military exercises. Further, article 42(2) requires that the laws and regulations of the State bordering a strait relating to transit passage not be applied so as to have the practical effect of denying, hampering or impairing the right of transit passage.
Innocent Passage in International Straits. Under article 45(1)(b), the regime of innocent passage, rather than transit passage, applies in straits used for international navigation that connect a part of the high seas or an EEZ with the territorial sea of a coastal State. There may be no suspension of innocent passage through such straits, and there is no right of overflight in such straits. These so-called "deadend" straits include Head Harbour Passage leading through Canadian territorial sea to the United States' Passamaquoddy Bay.
Under articles 38(1) and 45(I)(a), the regime of non-suspendable innocent passage also applies in those straits formed by an island of a State bordering the strait and its mainland, where there exists seaward of the island a route through the high seas or EEZ of similar convenience with regard to navigational and hydrographical characteristics.
International Straits Not Completely Overlapped by Territorial Seas. The effect of article 36 is that ships and aircraft transiting through or above straits used for international navigation which are not completely overlapped by territorial seas and through which there is a high seas or EEZ corridor suitable for such navigation enjoy the high seas freedom of navigation and overflight while operating in and over such a corridor.
Moreover, if the high seas route is not of similar convenience with respect to navigational or hydrographical characteristics, the regime of transit passage applies within such straits. Thus, for example, a submarine may transit submerged through the territorial sea in a strait not completely overlapped by territorial seas where the territorial sea route is the only one deep enough for submerged transit.
"Straits Used for international Navigation." Under the Convention, the criteria in identifying an international strait is not the name, the size or length, the presence or absence of islands or multiple routes, the history or volume of traffic flowing through the strait, or its relative importance to international navigation. Rather, the decisive criterion is its geography: The fact that it is capable of being used for international navigation to or from the high seas or the EEZ.
The geographical definition contemplates a natural strait and not an artificially constructed canal. Thus, the transit passage regime does not apply to the Panama and Suez Canals.
Legal Status of Waters Forming international Straits. The regime of passage through international straits does not affect the legal status of these waters or the sovereignty or jurisdiction of the States bordering straits (article 34(1)). Article 34(2) requires States bordering straits to exercise their sovereignty and jurisdiction in accordance with Part III and other rules of international law. States bordering straits must not impede the right of transit passage.
