the principle of the exclusiveness of flag State jurisdiction on the high seas may be varied in three situations. First, it is possible to depart from the principle of the exclusiveness of flag State jurisdiction by specific treaties.
A particular example is the regulation of illicit traffic in narcotic drugs or psychotropic
substances by sea. Second, the issue arises as to whether or not the interference with foreign
vessels on the high seas can be justified by self-defence. Third, consideration must be given
to interception of vessels on the high seas for counter-migration purposes.
(a) The Regulation of Illicit Traffic in Narcotic Drugs or Psychotropic Substances
The use of private vessels for illicit traffic in narcotic drugs has long been a serious problem.
This problem has been addressed by a series of treaties, including:
• The 1961 Single Convention on Narcotic Drugs,
• The 1971 Convention on Psychotropic Substances,
• The 1988 UN Convention against Illicit Traffic in Narcotic Drugs and Psychotropic
• The 1995 Council of Europe Agreement on Illicit Traffic by Sea (hereinafter the Council of
• The 2003 Agreement Concerning Co-operation in Suppressing Illicit Maritime and Air
Trafficking in Narcotic Drugs and Psychotropic Substances in the Caribbean Area
(hereinafter the 2003 Caribbean Agreement), and
• The 2008 CARICIM Maritime and Airspace Security Co-operation Agreement.
In addition, there is an array of bilateral treaties on this subject.
Article 27(1)(d) of the LOSC provides the coastal State’s criminal jurisdiction on board a
foreign ship passing through the territorial sea for the suppression of illicit traffic in
narcotic drugs or psychotropic substances. Furthermore, Article 108(1) of the LOSC places
an obligation upon all States to cooperate in the suppression of drug smuggling at sea.
Under Article 108(2), any State which has reasonable grounds for believing that a ship
flying its flag is engaged in illicit traffic in narcotic drugs or psychotropic substances may
request the cooperation of other States to suppress such traffic. Yet the LOSC provides no
basis for boarding drug smuggling vessels by non-flag States on the high seas.
At the multilateral level, the 1988 UN Convention against Illicit Traffic in Narcotic Drugs
and Psychotropic Substances is of particular importance. This Convention aims to
promote cooperation among the Parties in order to address more effectively the various
aspects of such traffic that have an international dimension. Of note here is the boarding
and searching of foreign suspected vessels on the high seas. Under Article 17(3) of the 1988
Convention, a Party which has reasonable grounds to suspect that a vessel exercising
freedom of navigation flying the flag of another Party is engaged in illicit traffic may so
notify the flag State, request confirmation of registry and, if confirmed, request authorisation
from the flag State to take appropriate measures in regard to that vessel. In this case,
pursuant to Article 17(4), the flag State may authorise the requesting State to, inter alia: (a)
board the vessel; (b) search the vessel; and (c) if evidence of involvement in illicit traffic is
found, take appropriate action with respect to the vessel, persons and cargo on board.
Action under Article 17(4) is to be carried out only by warships or military aircraft, or other
governmental ships in accordance with Article 17(10). A Party which has taken any action
in accordance with Article 17 is under a duty to promptly inform the flag State concerned of
the results of that action.
Article 17 was further amplified by the 1995 Council of Europe Agreement. Under Article
6 of the Agreement, where the intervening State has reasonable grounds to suspect that a
vessel flying the flag of another Party is engaged in the commission of a relevant offence,
the intervening State may request the authorisation of the flag State to stop and board the
vessel in waters beyond the territorial sea of any Party and to take some or all of the other
actions specified in this Agreement. The flag State is to communicate a decision thereon
as soon as possible and, wherever practicable, within four hours of receipt of the request in
accordance with Article 7. Having received the authorisation of the flag State, the intervening
State may take actions specified in Article 9(1), such as stopping and boarding the
To give another example: Article 16(1) of the 2003 Caribbean Agreement provides:
[W]hen law enforcement officials of one Party encounter a suspect vessel claiming the
nationality of another Party, located seaward of any State’s territorial sea, this Agreement
constitutes the authorisation by the claimed flag State Party to board and search the suspect
vessel, its cargo and question the persons found on board by such officials in order to determine
if the vessel is engaged in illicit traffic.
It follows that the ratification of the Agreement itself furnishes an a priori authorisation for
boarding foreign suspected vessels on the high seas. This procedure can enhance expediency
in law enforcement since there is no need for the intervening States to wait for the
response from the flag State with regard to the request of authorisation for boarding.
Some bilateral treaties also provide a priori authorisation for the boarding of ships for the
purpose of the suppression of illicit drug traffic at sea. It is important to note that, under
the above mentioned treaties, interception of foreign vessels on the high seas relies on the
authorisation of the flag State. In this sense, these treaties do not change the principle of
exclusive jurisdiction of the flag State.
(b) Self-defence on the High Seas
There is no doubt that States have the inherent right of self-defence under international
law, but can interference with foreign ships on the high seas be justified by the right of
self-defence? After World War II, States have sometimes justified interference with foreign
vessels on the high seas on the basis of the right of self-defence. During the Algerian
Emergency between 1956 and 1962, for example, the French Navy undertook to visit and
search a considerable number of foreign ships on the high seas with a view to stemming the
flow of arms and munitions into Algeria. Nonetheless, most of the States whose ships were
affected by the French naval operation protested, and, in some cases, gave rise to serious
diplomatic difficulties, particularly between France and the Federal Republic of
Another well-known incident concerns the Cuban Quarantine in the 1962 Cuban missile
crisis. On 23 October 1962, the Organization of American States called for the withdrawal
of missiles from Cuba, and recommended that the Member States take all measures under the Inter-American Treaty of Reciprocal Assistance. Pursuant to this resolution, US President Kennedy immediately ordered that the United States Navy interdict the delivery of offensive weapons to Cuba and, thus, any ship proceeding towards Cuba might be ordered to submit to visit and search on the high seas. In order to justify this operation, the myriad
possible justifications, including the right of self-defence under Article 51 of the UN
Charter, were submitted. Nonetheless, it appears debatable whether the US operation could
be fully justified on the basis of self-defence.
The ILC was cautious about including a rule governing self-defence in the Geneva
Convention on the High Seas ‘mainly because of the vagueness of terms like “imminent
danger” and “hostile acts”, which leaves them open to abuse’. One can say that the
validity of the exercise of the right of self-defence on the high seas is to be judged on a
case-by-case basis in accordance with the international law of self-defence, in particular
Article 51 of the UN Charter.