The nationality of a vessel, shown by the vessel’s flag or in former times by another symbol, has played a role since ancient times. The flagging out of a vessel has been practised since the 12th century. It was done for political, military or commercial reasons. It was up to the discretion of a State to grant a vessel the right to fly its flag, as held in the two well-known judgments The Montijo (1875) and The Muscat Dhows (1905). Since the beginning of the 20th century, economic considerations have encouraged a shipowner to apply to be given the right to fly the flag of another State than his own. The State of Panama took the lead and allowed totally foreign-owned Panamanian companies to have their ships sailing under the Panamanian flag (1916). In particular US shipping companies made use of this opportunity mainly in order to decrease manning costs. After the Second World War, nearly one half of the world’s commercial fleet sailed under those “flags of convenience” due to the possibility granted by various States (such as Liberia and Cyprus) of registering vessels in those countries’ “open registers”. Since about 1930, the process of flagging out a vessel has been increasingly criticized. These criticisms were initially founded upon the social situation of crews serving in such vessels and the “unfair” competition of such vessels with vessels flying the flag of their owners’ home country. Later, safety aspects with regard to the technical standards of those vessels became the main concern and, thus, the reason for discussing the vessels under flags of convenience within the United Nations.

The author follows and describes the development of the customary law on the nationality of flags and on its recognition by other States. On the one hand, there is the freedom of a State to grant to a vessel the right to fly its flag (as shown by the Muscat Dhows judgment). On the other hand, nearly all national laws on the right to fly the country’s flag presuppose a certain relationship existing between the vessel and the State whose flag it flies. This relationship was said to be formed by what was called the “genuine link”, a maxim developed in the Nottebohm judgment (deciding on the true nationality of a person, 1905), wherein the “real and effective nationality” was held to be of the essence. Though, in the author’s opinion, the maxim elaborated by the court in that case cannot mutatis mutandis be applied to a vessel, this feature of a “genuine connection” was nevertheless adopted when drafting the Geneva Convention on the High Seas (1958), in the UN Convention on the Law of the Sea (1982) and in the UN Convention on Conditions for Registration of Ships, adopted 1986. As the author explains, the function and the exact meaning of the term “genuine link” are not clearly defined, and no agreement has been reached on its true meaning. Only one thing is obvious: this relatively narrow relationship between vessel and flag State is supposed to enable that State to have the “effective exercise of jurisdiction and control” over a particular vessel. A practical result of that rule has been found in international labour law, where courts have sometimes refused to apply the law of the flag Stage since no such genuine link had been found (cf. A. D. Hughes, Casebook on Carriage of Goods by Sea (Blackstones, 1994) reviewed in [1995] LMCLQ at 421). Perhaps due to this relative ineffectiveness of the “genuine link” doctrine, endeavours have been