The freedom of the high seas is one of the cornerstone principles of the international maritime regime: the high seas are open to all States, and as a corollary, "no State may lawfully allege to subject any part of [them] to its jurisdiction." 2 However, this does not imply that no legal norms apply on the high seas.

On the contrary, when it comes to the high seas, where a variety of activities might take place, from simple ship transit to deep-sea mining, the necessity for every individual and every space to be subject to the authority of a State that can exert control is no less pressing.

'[t]he absence of any authority,' according to the International Law Commission (ILC), the absence of any authority over ships sailing the high seas would lead to chaos.[1] The State most directly related to the ship, i.e., the flag State, has jurisdiction over the high seas as a whole, but not over the vessels that sail them.

This rule is now formalised in UNCLOS Article 92, which states that the flag State's authority is exclusive. Indeed, the rule states that "[s]hips shall sail under the flag of only one State and shall be subject to its exclusive jurisdiction on the high seas, unless in rare instances expressly allowed for in international treaties or in this Convention." UNCLOS is without a doubt one of the most successful attempts at international law codification,4 with an almost global reach, having been ratified by 168 parties as of today. Furthermore, Art. 92 is frequently used and considered to reflect the Customary International Law[2].

The term 'jurisdiction' refers to the 'right of nations (and, for that matter, international organisations like the United Nations or the European Union) to authoritatively announce what the law is in their area and how it will be enforced' in its broadest sense.

However, jurisdiction can be exercised in a variety of ways:

1. Through legislation ('jurisdiction to prescribe');
2. Through procedures for identifying rule violations and the consequences of those violations ('jurisdiction to adjudicate'); and
3. Through mechanisms aimed at forcing compliance with those rules or punishing non-compliance ('jurisdiction to enforce').

Some scholars merely distinguish between prescriptive and enforcement jurisdiction, with the former including adjudicative authority. What matters, though, is that States' jurisdiction States' jurisdiction can manifest itself in different forms[3].

Because Art. 92 UNCLOS does not define the phrase 'jurisdiction,' it has been debated whether it refers to all of the aforementioned categories of jurisdiction or merely the jurisdiction to enforce. In other words, whether the principle of exclusive flag-State jurisdiction only prohibits non-flag States from enforcing their legal rules on ships sailing the high seas (i.e., obstructing or otherwise interfering with the actual movement of such ships through coercive acts) or also prohibits the exercise of prescriptive and adjudicative powers over conduct taking place on board foreign ships on the high seas is a point of contention.

The topic of which country has jurisdiction over ships on the high seas is a long-standing one. The PCIJ issued its pivotal decision in the 'Lotus' case[4] in 1927 on the subject. Despite the fact that the case involved a collision involving ships flying different colours, it provided important insights into the general issue of what qualifies a State to exercise its jurisdiction, and therefore became a 'paradigmatic judgement' that established the tone for everything that came after'.

The PCIJ concluded, as is well known, that while no State can claim to have jurisdiction over foreign ships on the high seas, States can have jurisdiction over acts that occur on board in their own territory, unless there is an unusual rule to the contrary.

The problem does not appear to be purely theoretical; rather, it looks to be of tremendous practical consequence. In fact, while a State's legal system can only be enforced within its borders, it has the right - to a degree - to attach legal consequences to activities performed abroad and/or by foreigners under general international law. Indeed, the criteria that might be used to establish jurisdiction are divided into four categories:

1. Territoriality;
2. Nationality;
3. The idea of protection; and
4. Universality[5].

However, there must be a distinction drawn between prescriptive/ adjudicative and enforcement jurisdiction. In the case of the latter, it is widely believed that states are only permitted to use it within their own borders, and that any enforcement effort conducted on the territory of another country would require the approval of that country.

Prescriptive/adjudicative jurisdiction can be based on any of the four characteristics listed above, with territoriality and nationality (at least active nationality) being the most well-established in general international law.

From 'Lotus' to 'Enrica Lexie': Exclusive Flag-State Jurisdiction in the Case Law of International Courts and Tribunals
Only a few international tribunals have directly addressed the topic of the scope of state powers on the high seas, the most notable of which is the 'Lotus' case. The case involved the collision of the French mail steamer 'Lotus' with the Turkish collier 'Boz-Kourt,' which resulted in the deaths of eight Turks.

When the 'Lotus' arrived in Constantinople, Turkish officials launched an investigation and arrested Lieutenant Demons, the 'Lotus's officer of the watch and a French national. He was then sentenced to eighty days in prison and a fine of twenty-two pounds. France claimed that the Turkish authorities had broken international law by commencing criminal procedures against Lieutenant Demons, claiming that only France, as the 'Lotus' flag State, was authorised to do so.

As is well-known, the PCIJ found that Turkey had not violated international law; this finding was premised on the distinction between enforcement jurisdiction and other types of jurisdictions. Indeed, the Court stated that apart from certain special cases which are defined by international law - vessels on the high seas are subject to no authority except that of the State whose flag they fly. In virtue of the principle of the freedom of the seas, that is to say, the absence of any territorial sovereignty upon the high seas, no State may exercise any kind of jurisdiction over foreign vessels upon them[6].

Despite the reference to 'any kind of jurisdiction', the Court also noted that 'it by no means follows that a State can never in its own territory exercise jurisdiction over acts which have occurred on board a foreign ship on the high seas. A corollary of the principle of the freedom of the seas is that a ship on the high seas is assimilated to the territory of the State the flag of which it flies, for, just as in its own territory, that State exercises its authority upon it, and no other State may do so.

All that can be said is that by virtue of the principle of the freedom of the seas, a ship is placed in the same position as national territory; but there is nothing to support the claim according to which the rights of the State under whose flag the vessel sails may go farther than the rights which it exercises within its territory properly so called'[7].

Nonetheless, a PCA arbitral panel created in line with Annex VII UNCLOS to settle the dispute between Italy and India over the 'Enrica Lexie' incident accepted the findings in M/V 'Norstar.' The dispute began when two Indian fishermen were shot by two Italian marines on board the Italian-flagged oil tanker 'Enrica Lexie.'

The event took place in India's Exclusive Economic Zone (EEZ), which is covered by Art. 92 UNCLOS due to a reference in Art. 58 para. 2 ('Articles 88 to 115 and other important principles of international law apply to the exclusive economic zone inasmuch as they are not incompatible with this Part'). The 'Enrica Lexie' arrived after the shooting entered Indian territorial waters and the two marines were later arrested by Indian authorities and accused of murder. In 2015, Italy instituted proceedings against India under Annex VII UNCLOS, alleging, inter alia, that India did not have jurisdiction over the incident as the only State entitled to prosecute the marines was the flag State, meaning Italy itself; in addition, Italy claimed that the marines enjoyed functional immunity[8].

The rulings show that the scope of a state's authority over ships sailing the high seas is a contentious subject today. Indeed, following a period in which the 'Lotus' viewpoint dominated and was approved by the majority of researchers, the 'Norstar' and 'Enrica Lexie' decisions flipped the situation, revealing the necessity for a thorough re-evaluation of the issue. In the following paragraphs, an attempt will be made to interpret Art. 92 UNCLOS, beginning with a reading of this provision that takes into account the Articles that provide exceptions to the rule of exclusive flag-State jurisdiction, as well as their drafting history.

Art. 92 UNCLOS in Context: Exceptions that Prove the Rule?
The first thing an interpreter trying to elucidate the meaning of Art. 92 UNCLOS would certainly note is the fact that such provision uses the term 'jurisdiction' without further specifications. This could suggest that the ordinary meaning of the term refers to all types of jurisdictions. However, it would be erroneous to let the matter rest here. Actually, several contextual elements can be derived from provisions other than Art. 92 UNCLOS and should be taken into account in the interpretation of the latter.

In this respect, one cannot but notice that other UNCLOS provisions are usually clear in specifying whether they refer to the power of States to adopt laws and regulations or to the power to enforce them. An example of a provision referring to prescriptive powers of States can be found in Art. 42 para.1 UNCLOS.

However, a closer examination of the Convention as a whole reveals other contextual aspect that hint to an alternative interpretation of UNCLOS Art. 92. Because Art. 92 UNCLOS clearly permits for exceptions to the rule of exclusive flag-State jurisdiction established by UNCLOS, the clauses enshrining such exceptions should be considered. They're mostly found in Arts 105, 109, 110, and 111. These clauses are unmistakably enforcement-oriented.

The provisions incorporating the exceptions giving policing rights to warships over foreign vessels are clearly of an enforcement nature. Indeed, Art. 43 codifies the right to seize a pirate ship or aircraft, or a ship taken by piracy and under the control of pirates, arrest the persons and seize the property on board; it was later transposed into Art. 19 of the 1958 Geneva Convention and then into the aforementioned Art. 105 UNCLOS;

Similarly, Art. 46 - concerned with the right of visiting and boarding vessels on the high seas - later became Art. 22 of the 1958 Geneva Convention and then, with modifications, Art. 110 UNCLOS. Lastly, Art. 47 on hot pursuit formed the basis for Art. 23 of the 1958 Geneva Convention and then, with modifications, for Art. 111 of UNCLOS. Later, the concerns surrounding the 'Lotus' rule were also shared by the ILC which, in 1956, adopted a very similar wording in Art. 35 of the Articles Concerning the Law of the Sea.54 Art. 35 UNCLOS provided the basis for Art. 11 of the 1958 Geneva Convention on the High Seas, which later became Art. 97 UNCLOS.

Finally, the normative context of Art. 92 UNCLOS - interpreted in light of its drafting history - reveals that the principle of exclusive flag-State jurisdiction was never intended to limit other States' capacity 'to apply a particular juridical order to the appraisal of a legal situation on the high seas,'[9] but only to limit their ability to enforce such legal order while the ship is sailing the high seas. This is due, first and foremost, to the principle's exceptions, which are of an enforcement character, as evidenced by their drafting history and the ILC's activity.

Exclusive Flag-State Jurisdiction in State Practice
A contextual and historical reading of Art. 92 UNCLOS implies an interpretation that only prescribes the exclusivity of enforcement flag-State jurisdiction while the ship is on the high seas, as argued in the previous Section. This conclusion is supported by state practise; the majority of this practise relates to criminal jurisdiction, as the prevention and repression of crimes committed in areas beyond national jurisdiction, such as the high seas, is the area in which States have felt the most pressing need to cooperate and adopt common norms.

To begin with, there are several accords whose contents appear to establish that exclusive flag-State jurisdiction exclusively applies to enforcement actions initiated against ships sailing the high seas. Even when such behaviour is carried out on board foreign-flagged boats, these treaties often impose on States Parties the need to criminalise it and to take adjudicative jurisdiction over it.

Such accords are relevant in assessing the meaning of Art. 92 UNCLOS under Art. 31 para. 3 lit. b) VCLT since they have been ratified by a large number of States that have also ratified UNCLOS and deal with the problem of jurisdiction with its interpretation. It is true that, in establishing the principle of exclusive flag-State jurisdiction, Art. 92 UNCLOS allows for exceptions "expressly allowed for in international treaties."

The SUA Convention, on the other hand, does not appear to be one of those exclusions. Indeed, the SUA Convention's Art. 9 expressly reaffirms the idea of enforcement jurisdiction exclusivity, stating that "nothing in this Convention shall affect in any way the rules of international law pertaining to the competence of States to exercise investigative or enforcement jurisdiction on board ships not flying their flag."

This paragraph, when read in connection with the preamble, recognises the "need for all States to scrupulously comply with laws and principles in combatting unlawful activities against the safety of marine navigation & principles of general international law' - seems to support a narrow reading of Art. 92 UNCLOS rather than providing an exception to it.

In conclusion, State practice supports the idea that States in no way feel themselves as being prevented from exercising prescriptive/adjudicative jurisdiction over facts occurred on the high seas and on ships not flying their flag, where there is a valid jurisdictional basis under general international law.

Conclusion
The exclusive jurisdiction of flag-States over ships sailing the high seas is a long-standing and widely accepted principle guiding the international maritime regime, defined in UNCLOS Art. 92. The question of the scope of this exclusive jurisdiction, however, has yet to be resolved. On the contrary, the dispute over the nature of states' authority over foreign ships travelling the high seas has resurfaced in the wake of the 'Norstar' and 'Enrica Lexie' rulings, which welcomed a viewpoint previously held by only a small number of academics.

This paper has argued that exclusive flag-State jurisdiction on the high seas only encompasses enforcement jurisdiction, meaning the right to interfere - through coercive actions - with the actual movement of a ship. It goes without saying that this does not mean that States, in exercising their prescriptive and adjudicative powers over ships sailing the high seas, can act as they see fit.

It only signifies that the facts occurred on the high seas may fall under the prescriptive and adjudicative jurisdiction of a State other than the flag State that can validly claim the existence of a jurisdictional basis recognised by international law. Furthermore, the assertion of jurisdiction without a valid connecting factor can still be a violation of UNCLOS.

Some authors have suggested that the exercise of prescriptive powers without a valid legal basis can represent a breach of the freedom of navigation enshrined in Art. 87 UNCLOS.79 Moreover, it is also obvious that the title for the exercise of jurisdiction by non-flag States can never be territoriality. Indeed, to extend the territorial jurisdiction over the high seas would result in a violation of the already mentioned Art. 89 UNCLOS, according to which 'no State may validly purport to subject any part of the high seas to its sovereignty'.

Thus, to exclude prescriptive and adjudicative powers of non-flag States could potentially lead to such situations escaping the jurisdiction of any State and to the high seas being an under-regulated area.

End-Notes:

1. ILC, 'Articles Concerning the Law of the Sea with Commentaries', ILCYB 1956, Vol. II, (279), Commentary to Art. 30, para. 1.
2. 5 PCA, The 'Enrica Lexie' Incident (Italy v. India), award of 21 May 2020, para. 467. See also Douglas Guilfoyle, 'The High Seas' in: Rothwell, Oude Elferink, Scott and Stephens (eds) (n. 4), 203-225 (209); Doris König, 'Flag of Ships' in: Rüdiger Wolfrum (ed.), MPEPIL (online edn, Oxford: Oxford University Press 2009), para. 25.
3. See, e. g. Christopher Staker, 'Jurisdiction' in: Malcolm D. Evans (ed.), International Law (5th edn, Oxford: Oxford University Press 2018), 289-315 (292-293).
4. PCIJ, The Case of the S. S. 'Lotus' (France v. Turkey), judgement of 7 September 1927, PCIJ Collection of Judgments 1927, 4
5. Cedric Ryngaert, Jurisdiction in International Law (2nd edn, Oxford: Oxford University Press 2015), 101; Oxman (n. 7); Staker (n. 8), 294.
6. PCIJ, The Case of the S. S. 'Lotus' (n. 9), 25.
7. PCIJ, The Case of the S. S. 'Lotus' (n. 9), 25.
8. For a thorough analysis of the case and the award see Natalino Ronzitti, 'Il caso della Enrica Lexie e la sentenza arbitrale nella controversia Italia-India', Riv. Dir. Int. 103 (2020), 937-958; Giuseppe Cataldi, 'The Enrica Lexie Award Amid Jurisdictional and Law of the Sea Issues
9. Memorandum on the Regime of the High Seas (n. 48), 18.