Seizing stateless smuggling vessels on the Mediterranean High Seas

Abstract

The EUNAVFOR MED anti-smuggling mission, Operation Sophia, ended in March 2020 and is largely viewed to have failed in its objective of ‘disrupting the business model’ of migrant smugglers in the Mediterranean region. The mission relied on purported enforcement powers in the 1982 United Nations Convention on the Law of the Sea and the 2000 Migrant Smuggling Protocol to seize and destroy stateless smuggling vessels on the high seas. Despite repeated claims to such powers by the European Union, neither treaty provides a strong jurisdictional basis for seizing stateless smuggling vessels outside territorial waters. However, ambiguous drafting in the Migrant Smuggling Protocol viably permits some claims to extraterritorial enforcement jurisdiction over stateless smuggling vessels on the high seas, and the European Union has relied on this ambiguity to tackle migrant smuggling. This article argues that the recent European Union anti-smuggling operations, most notably Operation Sophia, have reinterpreted the ambiguous term ‘appropriate measures’ in the Migrant Smuggling Protocol as permitting the states parties to exercise enforcement jurisdiction over stateless smuggling vessels at sea.

1. Introduction

At midnight on 19 April 2015, an overcrowded fishing boat carrying hundreds of migrants and asylum seekers capsized on the high seas south of the Italian island of Lampedusa. ¹ Several days after the tragic accident, which killed nearly 800 women, men, and children, the Council of the European Union met to discuss migration in the Mediterranean region. ² The EU had been reluctant to support Italy’s search and rescue operation, Operation Mare Nostrum, in recent years, fearing that it acted as a pull-factor for irregular migration. ³ Despite this, the rising death toll finally galvanized the EU member states into action to prevent further loss of life. Rather than fund a humanitarian search and rescue operation, however, the Council committed to ‘strengthen its presence at sea, to fight the traffickers, to prevent illegal migrant flows and to reinforce internal solidarity and responsibility’. ⁴ To this end, the Council invited the High Representative of the EU for Foreign Affairs and Security Policy, Federica Mogherini, to begin preparations for a Common Security and Defence Policy naval operation to ‘disrupt trafficking networks, bring the perpetrators to justice and seize their assets’ in accordance with international law. ⁵

Just two months later, on 22 June 2015, the EU launched the Common Security and Defence Policy mission EUNAVFOR MED, also known as Operation Sophia. ⁶ Although performing search and rescue functions, the operation’s core mandate was to identify, capture, and destroy vessels and weapons used by migrant smugglers. By ‘disrupting the business model’ of human smuggling and trafficking networks, the Council Decision establishing the operation asserted, EUNAVFOR MED Operation Sophia would also ‘save lives’ and ‘strengthen border control’ at sea. ⁷ The operation was designed to take place in three phases. ⁸ The first phase was restricted to gathering intelligence on migrant smuggling networks in the Mediterranean region, while the second and third phases envisaged the interdiction and eventual destruction of migrant smuggling vessels on the high seas, and in Libyan territorial waters. ⁹

Between its launch in 2015 and its closure in 2020, EUNAVFOR MED Operation Sophia seized and destroyed hundreds of migrant smuggling boats on the high seas in the Mediterranean Sea, and detained the persons on board these vessels. However, the Council of the European Union legal document underpinning the mission left the international legal basis for these actions unclear. Specifically, Council Decision 2015/778 left open whether authority for such actions derived from UNCLOS, the 2000 Migrant Smuggling Protocol, or an anticipated Security Council resolution. ¹⁰ Yet none of these instruments expressly permit states to seize stateless smuggling vessels on the high seas. UNCLOS contains no enforcement powers over stateless vessels beyond board and search, and the Migrant Smuggling Protocol only ambiguously permits a boarding state party to take ‘appropriate measures’ in respect of stateless vessels confirmed to be engaged in the smuggling of migrants by sea. ¹¹ Moreover, the anticipated Security Council resolution, Resolution 2240 (2015), referred only to boarding and inspecting vessels suspected of being without nationality and engaged in migrant smuggling, but not to arrest or seizure.

Operation Sophia closed down in March 2020, ¹² yet the issue of maritime migrant smuggling has not faded from view. Since then, European states have continued to exercise extraterritorial coercive powers over stateless smuggling vessels at sea, despite the unsettled legal basis of these actions under international law. ¹³ This lack of clarity is problematic for several reasons. Firstly, without a valid legal basis, the legality of high seas arrests of migrant smugglers and seizure of smuggling vessels are challengeable before domestic courts and the European Court of Human Rights, which makes launching high seas multilateral counter-smuggling operations a high-risk strategy for states. ¹⁴ Secondly, the ambiguity surrounding high seas seizure creates a grey-zone for coastal states to take coercive action against boat migrants and asylum seekers, while avoiding domestic legal and political accountability processes. ¹⁵ Finally, the EU, as well as other destination states worldwide, continue to exercise enforcement powers extraterritorially in order to externalize migration control, ¹⁶ and avoid existing human rights and refugee protections. ¹⁷ In particular, high seas interdictions of smuggling boats, including push-backs and pull-backs, interfere with the internationally recognized right of all persons to leave a country, including their own. ¹⁸

Despite these concerns, this article argues that the recent EU anti-smuggling operations, most notably Operation Sophia, have reinterpreted the ambiguous term ‘appropriate measures’ in the Migrant Smuggling Protocol. Arguably, now, Article 8(7) of the Migrant Smuggling Protocol authorizes states to take coercive measures over intercepted stateless smuggling vessels beyond the board and search powers contained in UNCLOS. This article begins by briefly recounting the history of EUNAVFOR MED Operation Sophia (Section 2), before explaining the ambiguity of the Migrant Smuggling Protocol towards high seas interdiction of stateless smuggling vessels (Section 3) and the interplay between the rules regulating the exercise of enforcement jurisdiction found in the law of the sea and the law of state jurisdiction. The final section explores how recent state practice, particularly the EU anti-migrant smuggling operations, have created a new jurisdictional rule authorizing the seizure and destruction of stateless smuggling vessels on the high seas (Section 5), and notes the urgent need to strengthen human rights and refugee protections for people escaping poverty, conflict, and persecution by sea.

2. EUNAVFOR MED Operation Sophia: A mission without an international legal mandate?

The Mediterranean migrant crisis has highlighted the legal uncertainty surrounding the right of states to seize and destroy stateless smuggling vessels on the high seas under international law. ¹⁹ Since 2015, over 1.5 million people escaping conflict or poverty have reached Europe by sea. ²⁰ Increasing numbers of migrants and asylum seekers began making the perilous journey across the Mediterranean Sea after the Arab Spring protests began throughout North Africa in 2011, and the Syrian civil war. ²¹ Initially, most asylum seekers from Syria settled in neighbouring countries, but after Lebanon, Jordan, and Egypt stopped accepting refugees in 2014, greater numbers began crossing the Mediterranean Sea in an attempt to seek permanent settlement in Europe. ²² This increase in migrant movements overlapped with the collapse of the Libyan government after a coalition of Western states intervened in 2011, which left no police forces controlling border movements and Libya’s maritime search and rescue zone ungoverned. ²³

From the early days of the crisis, migrant smugglers used unregistered and unflagged vessels to smuggle migrants and asylum seekers across the Mediterranean Sea to Europe. ²⁴ Smugglers initially transported the migrants and asylum seekers on larger ‘mother ships’ across the high seas, before off-loading them onto smaller vessels when close to Italian or Maltese shores. ²⁵ The smugglers adopted this method to avoid arrest and prosecution, under the belief that local police authorities had no jurisdiction to seize stateless vessels operating on the high seas. ²⁶ The smuggler’s tactic proved tragically perilous, however, with the small boats and inflatable dinghies used for the final stage of the journey often capsizing at sea. ²⁷

In response to the rising death rate, the Italian government launched Operation Mare Nostrum in October 2013. ²⁸ Designed as a search and rescue mission, Operation Mare Nostrum deployed assets on the high seas reaching beyond Italy’s search and rescue zone. ²⁹ In this respect, the operation relied on international search and rescue powers to intercept stateless smuggling vessels at sea. However, the Italian government was unable to sustain the exorbitant costs of the domestically unpopular operation and closed it down in October 2014. ³⁰ The Frontex-led operation, Operation Triton, replaced Operation Mare Nostrum, but with a different mandate and reduced geographical scope. ³¹ Rather than provide search and rescue services, Operation Triton was mandated to aid EU member states in achieving ‘effective border control in the Mediterranean region’ and tackle other forms of cross border crime around Italy’s coastal waters. ³² Thus, in contrast to Operation Mare Nostrum, Operation Triton did not include search and rescue within its core mandate. Foreseeably, the number of deaths at sea increased under the new law enforcement mission, climaxing in the ‘black week’ of April 2015 when more than 1,200 adults and children drowned in the Mediterranean Sea between Libya and Sicily. ³³

This tragedy finally drove the Council of the European Union to take action to prevent further loss of life. ³⁴ However, rather than fund a humanitarian search and rescue mission, the EU decided to launch a ‘military crisis management operation contributing to the disruption of the business model of human smuggling and trafficking networks in the Southern Central Mediterranean’. ³⁵ Given the Council designed the operation as a law enforcement operation, rather than a humanitarian search and rescue mission, the EU legislator could not rely on international search and rescue duties to interdict stateless smuggling vessels on the high seas, or apprehend smugglers aboard. ³⁶ Instead, the EU legislator needed an alternative international legal basis to seize and destroy stateless smuggling vessels outside the territorial seas of its member states in the Mediterranean Sea. ³⁷

Notably, however, Council Decision 2015/778, which legally underpinned Operation Sophia, did not concretely specify the international legal basis enabling the operation’s naval ships to seize and destroy stateless smuggling vessels on the high seas of the Mediterranean Sea. When read closely, Article 2(2) of Council Decision 2015/778 does not actually assert that international law authorizes Operation Sophia to seize and destroy stateless smuggling vessels. ³⁸ Rather, the wording only notes that any action taken against smuggling vessels, with or without nationality, would be taken in accordance with international law. The preamble to Council Decision 2015/778 claimed that ‘on the high seas … states may interdict vessels suspected of smuggling migrants … where the vessel is without nationality, and may take appropriate measures against the vessel, persons and cargo’. More specifically, Article 2(2) of the Council Decision stated that EUNAVFOR MED would conduct the ‘boarding, search, seizure and diversion of vessels suspected of being used for human smuggling or trafficking, under the conditions provided for by applicable international law, including UNCLOS and the Protocol against the Smuggling of Migrants’, or any applicable United Nations Security Council Resolution.

According to the Politico-Military Group, who advised the Council of the European Union on the international legal issues for Operation Sophia, international law does not directly provide enforcement powers over stateless vessels on the high seas, beyond board and search. However, the Politico-Military Group advised that seizure of stateless smuggling vessels would nevertheless be possible under international law ‘provided that the warship conducting the seizure is so authorized under its own national law’. ³⁹ In other words, according to the Politico-Military Group, Article 8(7) of the Migrant Smuggling Protocol permits states to authorize the seizure of stateless smuggling vessels, which can form the basis of high seas action. Even so, a UN Security Council mandate would still be necessary to enable EUNAVFOR MED warships to seize stateless vessels where domestic authorization was lacking. In other words, the Council of Europe needed a Security Council resolution to fill the jurisdictional gap surrounding stateless vessels in the law of the sea. ⁴⁰

On 11 May 2015, High Representative Federica Mogherini requested the Security Council to authorize the Common Security and Defence Policy operation under Chapter VII of the UN Charter. ⁴¹ Despite the predominant use of unflagged and unregistered vessels in migrant smuggling in the Mediterranean region, ⁴² Resolution 2240 (2015) did not authorize the seizure and destruction of stateless vessels. For a period of one year, the Security Council only authorized member states to inspect, seize and take further action, including disposal, of flagged vessels being used for migrant smuggling or human trafficking from Libya, provided that the boarding member state had made good faith efforts to obtain flag state consent. ⁴³ In contrast, the single paragraph referring to stateless vessels only called upon member states to:

Inspect, as permitted under international law, on the high seas off the coast of Libya, any unflagged vessels that they have reasonable grounds to believe have been, are being, or imminently will be used by organized criminal enterprises for migrant smuggling or human trafficking from Libya, including inflatable boats, rafts or dinghies. ⁴⁴

Markedly, the Security Council did not expressly authorize the seizure and destruction of unflagged vessels on the high seas. ⁴⁵ Instead, paragraph 5 merely repeated the right to visit vessels that a warship suspects of being without nationality, actions that UNCLOS and the Migrant Smuggling Protocol already permit. ⁴⁶ This left EUNAVFOR MED warships without direct authorization to seize and destroy stateless smuggling vessels on the high seas, and arrest any suspected smugglers aboard. Instead, The Council of the EU had to rely on the ambiguous wording of the Migrant Smuggling Protocol for seizure powers over stateless smuggling vessels on the high seas.

Operation Sophia closed down in March 2020, yet the question of the legality of high seas interdictions of stateless smuggling vessels under international law remains. Since 2020, European destination states have proposed, planned, and executed numerous coercive actions against migrants and asylum seekers trying to reach Europe by sea. Frontex missions, along with co-operating EU member states, continue to interdict stateless smuggling ‘motherships’ in international waters. ⁴⁷ The United Kingdom planned to ‘push-back’ migrant boats from British coasts into French waters in the Channel, until stopped by public outcry, while Greek authorities have engaged in ‘drift-back’ actions in the Aegean Sea, towing rescued migrants out to sea on unnavigable rafters. ⁴⁸ And Italy and Malta have co-operated with the Libyan Coast Guard to ‘pull-back’ migrant boats in distress to Libya, where the migrants onboard were subject to human rights violations. ⁴⁹ Additionally, Italy has repeatedly prosecuted migrants and asylum seekers forced by smugglers to navigate smuggling boats across the Mediterranean Sea for aiding and abetting migrant smuggling. ⁵⁰ These on-going practices stress the urgent need to clarify which enforcement powers exactly fall within the scope of the vague term ‘appropriate measures’, and ensure robust accountability measures exist to prevent states from using instruments designed to combat transnational crime to externalize migration control.

3. Boarding and seizure in UNCLOS and the Migrant Smuggling Protocol

The EUNAVFOR MED mission relied on enforcement powers allegedly provided by UNCLOS and the Migrant Smuggling Protocol to board, seize and destroy stateless smuggling vessels on the high seas. However, as noted above, Council Decision 2015/778 does not explicitly state the international legal basis for high seas seizure of stateless smuggling vessels. While both UNCLOS and the Migrant Smuggling Protocol permit the states parties to board suspect vessels, neither treaty provides a strong jurisdictional basis for exercising enforcement jurisdiction over stateless smuggling vessels outside territorial waters. Neither instrument provides prescriptive criminal jurisdiction over high seas smuggling offences nor expressly permits the states parties to seize suspect vessels. Despite this, it is likely that the Council of the European Union sought to justify the seizure of stateless smuggling vessels through Article 8(7) of the Migrant Smuggling Protocol, which permits a boarding state party to take unspecified ‘appropriate measures’ in respect of stateless smuggling vessels.

UNCLOS codifies the foundational principle of mare liberum, the freedom of the seas, that has governed the high seas for almost half a millennium. ⁵¹ This principle is found in Article 87 (the high seas are open to all states) and Article 89 (no state may acquire or claim sovereignty over any part of the high seas). ⁵² As a general rule, the law of the sea prohibits states from exercising enforcement powers over non-national vessels located on the high seas, ⁵³ and within the Exclusive Economic Zones (EEZ) of states. ⁵⁴ However, the law of the sea provides several exceptions to this general rule, which have been relied upon by states to claim jurisdictional powers over stateless vessels. ⁵⁵ However, none of these exceptions clearly authorizes the extraterritorial seizure of stateless smuggling vessels on the high seas or within the EEZ. ⁵⁶

Most relevantly under the general law of the sea, UNCLOS permits any state to board a non-national ship suspected of being engaged in piracy, unauthorized broadcasting, the slave trade, or where the ship is suspected of being without nationality, or concealing its nationality from its flag state. ⁵⁷ Some scholars assert that this right of visit in Article 110 of UNCLOS implies subsequent seizure powers over stateless vessels. ⁵⁸ However, the text of UNCLOS provides little support for this claim. ⁵⁹ The Convention regulates boarding and seizure separately, as they constitute different exercises of enforcement jurisdiction. ⁶⁰ That is to say, that while the exercise of any boarding rights proceeds the exercise of any seizure rights, the one does not entail the other. The right of visit, as set out in UNCLOS, is investigatory and does not depend upon or grant further criminal jurisdiction over the suspect vessel. ⁶¹ This is demonstrated by the fact that UNCLOS only provides further enforcement powers over vessels engaged in piracy or unauthorized broadcasting despite permitting board and search for piracy, unauthorized broadcasting, the slave trade, and suspected statelessness. ⁶²

Instead, the asymmetrical allocation of boarding rights and enforcement jurisdiction in UNCLOS reflects the evolution of enforcement powers in the law of the sea in response to new threats and challenges. ⁶³ Historically, customary international law restricted the right of visit to vessels suspected of piracy on the high seas. ⁶⁴ States extended this right to vessels suspected of the slave trade during the drafting of the 1958 High Seas Convention to reflect the wide-ranging number of bilateral treaties on the subject, ⁶⁵ and again to vessels suspected of unauthorized broadcasting and vessels suspected of being without nationality during the drafting of UNCLOS in the late 1970s and early 1980s. ⁶⁶ The right to seize pirate vessels, found in Article 105 of UNCLOS, also derives from customary international law, which permits all states having asserted universal prescriptive jurisdiction over piracy offences to seize pirate vessels and prosecute any captured pirates. ⁶⁷ Additionally, the drafters of UNCLOS included a novel, and now largely redundant, right to arrest vessels and persons engaged in unauthorized broadcasting on the high seas to certain affected states and prosecute the alleged offenders before their domestic courts in response to pirate radio stations broadcasting from ships moored outside the territorial waters of European coastal states in the late 1950s and early 1960s. ⁶⁸

In contrast, the Migrant Smuggling Protocol does permit some enforcement action over stateless smuggling vessels beyond boarding. However, the drafting of the relevant provision leaves the scope of permissible enforcement action unclear. The Protocol establishes a co-operation regime between the states parties to combat migrant smuggling by sea. For stateless smuggling vessels, Article 8(7) provides that:

A State Party that has reasonable grounds to suspect that a vessel is engaged in the smuggling of migrants by sea and is without nationality or may be assimilated to a vessel without nationality may board and search the vessel. If evidence confirming the suspicion is found, that State Party shall take appropriate measures in accordance with relevant domestic and international law.

Unlike piracy and unauthorized broadcasting in UNCLOS, Article 8(7) does not expressly grant the boarding state the right to seize a stateless vessel on the high seas, or arrest any suspected smugglers on board that vessel and prosecute them before its national courts. Instead, Article 8(7) merely notes that the boarding state party shall ‘take appropriate measures’ in accordance with relevant domestic and international law. This leaves the intended scope of permissible action ambiguous and open to interpretation.

According to the Politico-Military Group, who advised the Council of the European Union on the international issues underpinning EUNAVFOR MED, the Migrant Smuggling Protocol does not directly authorize states to seize, disable or destroy stateless smuggling vessels. ⁶⁹ However, it does permit states to adopt laws authorizing the seizure of stateless smuggling vessels on the high seas. ⁷⁰ In other words, the measures taken against stateless vessels depend upon domestic authorization. However, this view implies a revision of the standard rules governing jurisdiction at sea, explained below, which limit extraterritorial exercises of prescriptive and enforcement jurisdiction. ⁷¹ Although the vague drafting leaves space open for this interpretation, nothing in the text or preparatory documents to the Migrant Smuggling Protocol suggests that the drafters intended to extend extraterritorial criminal jurisdiction to stateless smuggling vessels on the high seas.

Firstly, the travaux préparatoires and the non-authoritative interpretative guides make no mention of seizure powers over stateless smuggling vessels. ⁷² The Migrant Smuggling Protocol does not contain a definition of the term ‘appropriate measures’ or specify that enforcement actions, such as seizure and arrest, fall within its scope. Nor do the preparatory works or interpretative guides explain the term, or throw any light on its intended meaning. As noted above, UNCLOS does not provide seizure powers over stateless smuggling vessels, and while UNCLOS does permit its states parties to modify its jurisdictional rules by agreement, ⁷³ nothing in the travaux préparatoires indicate that the drafters intended to create a new legal rule permitting high seas enforcement action. The avoidance of express seizure and arrest powers in Article 8(7) instead suggests that no such powers exist under the law of the sea, and that the negotiating states were not yet prepared to extend enforcement jurisdiction to stateless vessels at the time of drafting. ⁷⁴

Secondly, the Migrant Smuggling Protocol does not oblige or encourage the states parties to establish prescriptive criminal jurisdiction over migrant smuggling offences committed on board stateless vessels on the high seas. The Protocol only requires each state party to criminalize migrant smuggling when committed inside its territory, on board a vessel flying its flag, or an aircraft registered under its domestic laws. ⁷⁵ Nor does the Protocol even encourage the states parties to establish jurisdiction over high seas smuggling offences, as it does for offences committed by or against a national of the state party. The silence of the Protocol towards stateless vessels is notable given the inclusion of an obligation to establish prescriptive jurisdiction over offences committed on board stateless vessels in the 1995 Council of Europe Agreement on Illicit Traffic at Sea, which was drafted just a few years previously. ⁷⁶ Had the drafters intended to provide high seas enforcement powers over stateless vessels, it is likely they would have clearly provided prescriptive jurisdiction as well, as done by the drafters of the 1995 Council of Europe Agreement on Illicit Traffic at Sea.

Finally, as Article 8(7) is not restricted to the high seas, it could be argued that the drafters selected the vague term ‘appropriate measures’ to encompass the range of enforcement powers already existing under the law of the sea. Unlike Article 110 in UNCLOS, Article 8(7) is not restricted to the high seas. ⁷⁷ States parties can make use of different enforcement powers depending on the location of the suspect vessel. For example, on the high seas, the term appropriate measures might refer to an obligation to inform other affected states parties about the location and direction of the suspect vessel; to continue surveillance of the suspect vessel; or to fulfil rescue obligations for smuggling vessels in distress. ⁷⁸ At the same time, beyond the high seas, the term might denote the right of coastal states to refuse stateless vessels access to their ports; to prevent non-innocent passage into territorial waters; or to prevent infringements of immigration regulations in the contiguous zone. ⁷⁹ Had the drafters intended to provide wide-ranging enforcement jurisdiction in Article 8(7), they could have copied the drafting of Article 105 or Article 108 of UNCLOS for piracy and unauthorized broadcasting, which provide unequivocal high seas seizure and arrest powers. Overall, the absence of express seizure and arrest powers in Article 8(7) suggests that the negotiating states were not yet prepared to extend enforcement jurisdiction to stateless vessels at the time of drafting.

Historically, states have been reluctant to expand extraterritorial state power at sea or to disturb the delicate jurisdictional balance established in UNCLOS. ⁸⁰ However, at the same time, states have been occasionally willing to fill jurisdictional gaps at sea by creating new enforcement powers, as seen in the treatment of unauthorized broadcasting in UNCLOS. ⁸¹ Thus, while the Migrant Smuggling Protocol does not provide any express seizure powers, the ambiguous term ‘appropriate measures’ arguably still leaves space for the future expansion of high seas enforcement powers. However, whether the term ‘appropriate measures’ can entail seizure powers depends not just upon the Migrant Smuggling Protocol or the law of the sea, but also upon the international law of state criminal jurisdiction.

4. Extraterritorial criminal jurisdiction over stateless smuggling vessels

Since the early 2000s, scholars have debated whether the Migrant Smuggling Protocol creates a new right of action in respect of stateless smuggling vessel on the high seas beyond the powers permitted under the UNCLOS right of visit. ⁸² However, scholars have struggled to explain how the term ‘appropriate measures’ in Article 8(7) can provide seizure rights over stateless vessels while remaining consistent with the general law of the sea and state criminal jurisdiction. ⁸³ Scholarly accounts fall into two broad categories, which each describe a different view of the interaction between state criminal jurisdiction and the law of the sea. However, this article argues that neither of these accounts can satisfactorily explain the recent EU anti-smuggling operations in the Mediterranean Sea coherently with the orthodox view of prescriptive jurisdiction. ⁸⁴ Instead, this article proposes a new theory of state criminal jurisdiction, which allows for a coherent explanation of state practice in the application of the Migrant Smuggling Protocol.

International law regulates the exercise of jurisdiction by states. For international lawyers, jurisdiction refers to the allocation of competences normally aligned to state authority. ⁸⁵ Legal theory standardly divides state jurisdiction into two, or sometimes three, categories of jurisdiction. ⁸⁶ The first category, prescriptive jurisdiction, refers to the authority of a state under international law to determine the substance and scope of regulating norms through legislation or court rulings. Put simply, the right to regulate. The second category, enforcement jurisdiction, refers to the right of states under international law to execute those rules through police, judicial or other executive action. The final category, adjudicatory jurisdiction, encompasses the authority of states (more specifically, of national courts) under international law to adjudicate disputes between parties and to adjudge violations of domestic laws. This general framework applies to all exercises of state criminal jurisdiction both on land and at sea, although several special rules additionally regulate the high seas. ⁸⁷

Despite this agreed framework, the question whether international law permits states to exercise enforcement jurisdiction over stateless vessels remains controversial, and divides scholarly opinion. ⁸⁸ Some scholars argue that any boarding state may seize stateless vessels on the high seas, as stateless vessels lack the protection of a flag state. ⁸⁹ More commonly, international legal scholars suggest that boarding states must justify any exercise of high seas jurisdiction according to a special permissive rule, as exists for piracy and unauthorized broadcasting. ⁹⁰ Additionally, scholars holding this view often note that boarding states require a prescriptive jurisdictional nexus to any offences committed on board a stateless vessel in order to validly exercise enforcement jurisdiction over such vessels. ⁹¹ Although not immediately obvious, these positions depend upon different views of state criminal jurisdiction, which reflects the unsettled nature of the existing theory underpinning this topic of international law.

As noted, the first view argues that any state may seize a stateless vessel on the high seas as it lacks flag state protection. ⁹² Two presumptions underlie this view, relating firstly to the law of the sea and secondly to state criminal jurisdiction respectively. Firstly, this view presumes that any state may exercise enforcement jurisdiction on the high seas, unless barred by the principle of exclusive flag state jurisdiction. ⁹³ According to this view, the right of visit creates an exception to the principle of exclusive flag state jurisdiction, which prevents interference by non-national ships on the high seas. If boarding reveals that no flag state exists, then the boarding state may take further enforcement action against the stateless vessel. This explanation supposedly explains the silence of UNCLOS and the ambiguity in the Migrant Smuggling Protocol to seizure rights, as these treaties only need to authorize the initial interference in a vessel suspected of being without nationality. However, this view ignores that the principle of freedom, which governs the high seas, prohibits states from exercising jurisdiction or control over the high seas unless expressly permitted by international law. ⁹⁴

Secondly, this view presumes that a state may exercise enforcement jurisdiction despite lacking prescriptive jurisdiction under international law. The United States Federal Court of Appeal affirmed this position in US v. Marino-Garcia, famously claiming that ‘international law permits any nation to subject stateless vessels on the high seas to its jurisdiction’. ⁹⁵ According to the Court, ‘[j]urisdiction exists solely as a consequence of the vessel’s status as stateless’. ⁹⁶ This runs against the grain of prevailing scholarly opinion, which holds that states need valid prescriptive jurisdiction under international law to exercise enforcement jurisdiction. As Brownlie has emphasized, ‘[i]f the substantive jurisdiction is beyond lawful limits, than any consequent enforcement jurisdiction is unlawful’. ⁹⁷ In other words, even if international law permitted boarding states to seize stateless vessels on the high seas, international law would still require the boarding state to have valid prescriptive jurisdiction over any smuggling offences committed on board the stateless vessel, ⁹⁸ which neither customary international law or the Migrant Smuggling Protocol provide. ⁹⁹

According to the second view, most notably elaborated by Churchill and Lowe, the law of the sea prohibits states from exercising any enforcement authority on the high seas unless justified by a specific permissive customary or conventional rule. ¹⁰⁰ Such rules can entail either a right of visit over suspect vessels or a right of seizure of vessels engaged in certain prohibited activities, such as piracy and unauthorized broadcasting. Applied to stateless vessels, this view restricts general enforcement powers to boarding and inspection under Article 110 of UNCLOS, unless the boarding state can prove a right of seizure derived from another treaty. While this view excludes a right of seizure over stateless vessels under customary international law, it leaves the door open for states to extend high seas enforcement jurisdiction to stateless smuggling vessels through international treaty-making. While Churchill and Lowe make no mention of prescriptive jurisdiction, they presumably still meant that any exercise of state jurisdiction would need to be valid under international law. ¹⁰¹

For many scholars, this second view still excludes most boarding states from taking further enforcement action against vessels confirmed to be stateless and engaged in the smuggling of migrants at sea, as most boarding states lack prescriptive jurisdiction over high sea smuggling offences. ¹⁰² According to the orthodox view of state criminal jurisdiction, international law only permits states to exercise prescriptive jurisdiction upon a number of grounds or ‘heads’ of jurisdiction. ¹⁰³ Drawing on the 1935 Harvard University research reports on ‘Jurisdiction with respect to crime’, most commentators agree that international law recognizes only several heads of jurisdiction to prescribe, namely territoriality and flag state jurisdiction, active nationality, passive personality, the protective principle, and universality. ¹⁰⁴ These heads of jurisdiction are often coalesced into a general principle that states require a ‘genuine connection between the subject matter of jurisdiction and the territorial base or reasonable interests of the state in question’ to assert prescriptive jurisdiction. ¹⁰⁵ According to this view, any exercise of enforcement jurisdiction not based upon a valid head of prescriptive jurisdiction will be unlawful under international law. ¹⁰⁶

However, pursuant to this interpretation, few EU member states participating in the EUNAVFOR anti-smuggling operations would be able to take action against stateless smuggling vessels, as neither customary international law nor the Migrant Smuggling Protocol clearly provide prescriptive jurisdiction over high seas migrant smuggling offences. The offence of migrant smuggling does not fall within the scope of the universality principle under customary international law, which is generally recognized to be limited to a handful of heinous crimes. ¹⁰⁷ Furthermore, the drafters did not remedy this gap by providing prescriptive jurisdiction over migrant smuggling offences committed on board stateless vessels, similar to flag state jurisdiction over offences committed on board national vessels. ¹⁰⁸ Thus, even presuming that Article 8(7) of the Migrant Smuggling Protocol provides seizure rights over stateless vessels, this theory of state jurisdiction would still exclude most states from exercising enforcement powers over stateless vessel on the high seas as they lack prescriptive jurisdiction under international law. ¹⁰⁹

However, high seas enforcement action against stateless smuggling vessels is feasible under a different account of state jurisdiction. Contrary to the prevailing scholarly opinion, this article argues that state jurisdiction simply mirrors the basic international principles of territorial integrity, equality of states and non-interference in domestic affairs. ¹¹⁰ Under this account, a state has the presumptive right to exercise jurisdiction unless prohibited by a general principle of international law. For prescriptive jurisdiction, the principle of non-interference limits states in extending their prescriptive jurisdiction beyond their borders, rather than the notion of permissive ‘heads’ of jurisdiction. That is to say, while states may legislate extraterritorially, states may not validly enact laws directly or indirectly interfering in the international or external affairs of any other state, without that state’s consent. ¹¹¹ This account matches the rules already accepted as regulating jurisdiction to adjudicate and enforce. That is, the law of state immunity, which embodies the equality of states under international law, constrains the exercise of adjudicatory jurisdiction by states, and the principle of territorial integrity restricts any exercise of enforcement jurisdiction by states. ¹¹²

This account harks back to the obiter discussion of state criminal jurisdiction by the Permanent Court of International Justice in the S.S Lotus case. ¹¹³ The case concerned whether Turkey’s prosecution of a French national for criminal negligence, which led to the collision between the Turkish steamer the Boz-Kourt and the French steamer the Lotus on the high seas, conflicted with a principle of international law. While the ratio centred on the specific jurisdictional rule governing collisions at sea, the Permanent Court also offered its opinion on the general structure of state criminal jurisdiction. The Permanent Court’s reasoning is notoriously vague and convoluted, ¹¹⁴ but appears to follow a three-step structure of general permission, prohibitive rule, and specific exceptions. Firstly, the Permanent Court explained, ‘restrictions upon the independence of states cannot therefore be presumed’. ¹¹⁵ For this reason, a state remains free under international law to exercise jurisdiction in its own territory, ‘over acts which have taken place abroad’. ¹¹⁶ However, this presumptive right is subject to certain prohibitive rules. While the Permanent Court did not specify the prohibitive rules applicable to prescriptive or adjudicative jurisdiction, it noted that the principles of territorial integrity and freedom of the seas limit the enforcement jurisdiction of states. Finally, the Permanent Court observed, certain ‘permissive rule[s] derived from international custom or from a convention’ provide exceptions to this secondary level of prohibitions, ¹¹⁷ such as the right of visit in UNCLOS or aut dedere aut judicare obligations found in international treaties addressing serious crime.

Under this view, any exercise of enforcement jurisdiction based upon an invalid exercise of prescriptive jurisdiction will still be unlawful under international law, but not because prescriptive and enforcement jurisdiction are logically dependent upon each other. ¹¹⁸ Rather, any exercise of enforcement jurisdiction by a state based upon a claim to prescriptive jurisdiction that unjustifiably interferes in the internal or external affairs of another state will be invalid, even if the state exercises that jurisdiction in its own territory or according to the law of the sea. Applied to the Migrant Smuggling Protocol, this account of jurisdiction leaves the states parties free to establish prescriptive jurisdiction over high seas migrant smuggling offences committed on board stateless vessels, unless that criminalization would interfere in the domestic affairs of any other state. In other words, states do not need to rely upon a customary or conventional ‘head’ of jurisdiction to criminalize extraterritorial migrant smuggling offences.

Under this account of state criminal jurisdiction, the term ‘appropriate measures’ in Article 8(7) of the Migrant Smuggling Protocol arguably extends the scope of enforcement action permitted to the states parties beyond the UNCLOS right of visit over stateless vessels. Firstly, the states parties remain free under international law to establish prescriptive criminal jurisdiction over offences committed by non-nationals on board stateless vessels on the high seas, as this is unlikely to interfere in the domestic affairs of other states. ¹¹⁹ Secondly, the phrase ‘appropriate measures in accordance with relevant domestic and international law’ permits any state party to take enforcement action against stateless smuggling vessels on the high seas or in a EEZ, as long as the enforcement action is properly authorized under its domestic law and compliant with international human rights norms. ¹²⁰ Thus, while the absence of express seizure and arrest powers suggests that the negotiating states were not yet prepared to extend enforcement jurisdiction expressly to stateless vessels at the time of drafting, the vague drafting of Article 8(7) arguably left space for the states parties to expand the meaning of the term ‘appropriate’ measures through subsequent practice.

5. Subsequent practice to the Migrant Smuggling Protocol

Over the last 20 years, the Western destination states, most notably the EU member states, have relied on the ambiguity in the Migrant Smuggling Protocol to claim extraterritorial enforcement powers over stateless smuggling vessels on the high seas, and have substantiated these claims through enforcement action, law reform and inter-state agreements. ¹²¹ Subsequent practice is an accepted tool of treaty interpretation that can shed light on the original intention of the drafters or evidence their evolving intentions. ¹²² Given international law recognizes this interpretive tool, this article argues that the recent EU anti-smuggling operations, most notably Operation Sophia, have reinterpreted the ambiguous term ‘appropriate measures’ in the Migrant Smuggling Protocol as permitting the states parties to exercise enforcement jurisdiction over stateless smuggling vessels at sea.

Subsequent practice is a well-established tool of treaty interpretation, codified in Article 31(3)(b) of the Vienna Convention of the Law of Treaties, which consists of conduct by one or more parties in the application of the treaty, after its conclusion, which clarifies the meaning of a treaty. ¹²³ While subsequent practice can illuminate the original intentions of the drafters, it can also evidence the evolving intentions of the parties to a treaty over time. ¹²⁴ In this way, subsequent practice allows treaty rules and obligations to adapt to changing technological, social and normative conditions, as well as redressing deficiencies in the treaty text or ineffective compromises made by the drafters. ¹²⁵ Subsequent practice is standardly accepted as interpreting and adjusting a treaty, although scholars debate whether it can legitimately amend or modify the original meaning. ¹²⁶ In any event, subsequent practice by the states parties to the Migrant Smuggling Protocol can clarify or adjust the meaning of the term ‘appropriate measures’ in Article 8(7).

Vague treaty drafting allows for even greater interpretative flexibility, as the line between interpretation of a previously unclear term and reinterpretation contrary to the original meaning of the drafters is blurred. ¹²⁷ As noted above, the travaux préparatoires do not indicate what the drafters of the Migrant Smuggling Protocol meant by the term ‘appropriate measures’. ¹²⁸ However, the drafters used the same term in Article 8(2) of the Migrant Smuggling Protocol to signify any coercive actions authorized by the flag state. While the repetition of the same term does not necessarily entail that the drafters intended to grant a right of action over stateless vessels, it does indicate that seizure falls within the ordinary meaning of the term. Furthermore, this interpretation accords with the object and purpose of the Protocol, which is to ‘prevent and combat the smuggling of migrants land, sea and air’ and to ‘deny safe havens to those who engage in transnational crime’. ¹²⁹ Given that no flag state has jurisdiction over stateless vessels, an interpretation of ‘appropriate measures’ as permitting seizure would guard against impunity for smugglers.

The EU legislator has repeatedly claimed that Article 8(7) of the Migrant Smuggling Protocol entitles the states parties to take enforcement action against stateless smuggling vessels on the high seas, and substantiated this claim through legislation and enforcement action. ¹³⁰ The 2014 Frontex Regulation, and the 2010 Council Decision before it, assert that the member states are entitled to seize stateless smuggling vessels on the high seas, and apprehend any person on board the vessel. According to the 2014 Frontex Regulation, the Migrant Smuggling Protocol permits EU member states to conduct the following actions: to seize stateless vessels and apprehend any persons on board; to order a stateless vessels to modify its course towards a destination outside the territorial waters or the contiguous zone; to escort the stateless vessels onto another navigational course; and to conduct the stateless vessels to a third country and hand over the persons on board to the authorities of that state. ¹³¹

Frontex missions subsequently relied on this EU legislation to stop and seize stateless smuggling ‘motherships’ on the high seas, and arrest the smugglers on board. ¹³² Since its establishment in 2004, the powers and competencies of the EU Border and Coast Guard Agency (Frontex) has expanded dramatically, such that Frontex now holds the largest budget of all EU agencies. ¹³³ Frontex currently supports various member states with border control, surveillance and search and rescue in the Mediterranean Sea, with Operation Poseidon covering the Greek sea borders with Turkey, Operations Minerva and Indalo assisting Spain in the Western Mediterranean, and Operation Themis assisting Italy in the Central Mediterranean. ¹³⁴ Over the last few years, these operations have enhanced their law enforcement focus, with an emphasis on ‘combating of cross-border crime’. ¹³⁵ To this end, these operations frequently intercept suspected stateless smuggling vessels on the high seas, and transfer detained smugglers to the co-ordinating member states. ¹³⁶

Furthermore, recent Italian and Spanish case law has upheld the claim that the Migrant Smuggling Protocol permits Frontex-operated warships to seize stateless smuggling vessels on the high seas, and transfer suspected smugglers to the participating EU member states for trial. ¹³⁷ Most notably, the Italian Court of Cassation found that the seizure of an unflagged and unregistered smuggling vessel on the high seas within the Mediterranean Sea, and the transfer of its crew to Italy, fell within the scope of Article 8(7) of the Migrant Smuggling Protocol. ¹³⁸ According to the Court, Article 110(1)(d) of UNLCOS did not provide Italy with the sufficient legal basis to assert criminal jurisdiction over the alleged migrant smuggler, Egyptian national Harabi Hani. ¹³⁹ Yet, the Court reasoned, the term ‘appropriate measures’ in the Migrant Smuggling Protocol did permit the boarding state, in this case Italy, to take coercive action against smuggling vessels and any suspects aboard. ¹⁴⁰

The recent EUNAVFOR MED Operation Sophia has further buttressed this interpretation of Article 8(7) of the Migrant Smuggling Protocol by seizing and destroying hundreds of stateless vessels found on the high seas. Between 2015 and 2017, Operation Sophia seized and destroyed 452 smuggling boats, and apprehended over 140 smugglers. ¹⁴¹ Migrant Smugglers adapted to ‘people being detained and the boats being apprehended’ by Operation Sophia, by sending out the migrants and asylum seekers alone on inflatable dinghies onto the high seas in the anticipation of rescue. ¹⁴² This meant that, in the end, the majority of seizures and arrests took place under international search and rescue powers, with Operation Sophia rescuing an estimated 45,000 migrants and asylum seekers during its operating time from June 2015 to March 2020. ¹⁴³ By 2018, the Operation began to fall apart. ¹⁴⁴ Italy threatened to block Operation Sophia’s naval assets from off-loading rescued migrants in its ports, and Germany subsequently suspended the involvement of its ships. ¹⁴⁵ However, by this time, the public and multilateral nature of the EU operation had arguably cemented the interpretation of the Migrant Smuggling Protocol as permitting high seas seizure. ¹⁴⁶

Few, if any, states parties have objected to this interpretation of the Migrant Smuggling Protocol, which suggests widespread acceptance of, or acquiescence, to high seas seizure. Subsequent practice in the application of a treaty requires the active practice of at least some states parties to the treaty in question and acquiescence by the other states parties. ¹⁴⁷ While only some EU member states participated in Operation Sophia, no other states parties have publicly opposed the seizure and destruction of stateless smuggling vessels by EUNAVFOR MED warships. Notably, the Security Council did not expressly confirm this interpretation of the Protocol by calling upon member states to seize stateless smuggling vessels on the high seas, which, had they done so, would have crystalized the term ‘appropriate measures’ as granting high seas enforcement powers. Yet, at the same time, the Security Council meeting records do not evidence any objections by its member states concerning this interpretation at the time or subsequent to the extension of the mandate. ¹⁴⁸ Given the multilateral and public nature of the EU actions, the absence of objections from states parties not participating in Operation Sophia suggests that they have tacitly agreed to the interpretation of ‘appropriate measures’ as permitting seizure powers. ¹⁴⁹

Finally, it should be noted that valid jurisdiction under international law is not sufficient for an exercise of enforcement jurisdiction to be lawful under international law. International law still requires the boarding state party to have validly established prescriptive jurisdiction over high seas migrant smuggling offences in its domestic criminal code before taking enforcement action against stateless smuggling vessels. From an inter-state perspective, international law only requires that states do not interfere in the internal or external affairs of any other state, or breach any other prohibitive rule of international law, when establishing or exercising criminal jurisdiction. However, international human rights law adds another layer of protection for individuals. In particular, the principle of legality prohibits states from taking enforcement action in respect of any act or omission that did not constitute a criminal offence under national or international law at the time it was committed. ¹⁵⁰ In regards to high seas migrant smuggling, this means that states may not rely directly on the vague term ‘appropriate measures’ in Article 8(7) of the Migrant Smuggling Protocol to seize stateless smuggling vessels or arrest suspected smugglers aboard. Instead, any boarding state party needs to first establish prescriptive jurisdiction over the relevant extraterritorial offences and clearly authorize its law enforcement agencies to take high seas action before seizing stateless smuggling vessels on the high seas or in an EEZ.

6. Conclusion

EUNAVFOR MED Operation Sophia closed down in March 2020, leaving the question of the mission’s legality under international law unanswered. The UN Security Council did not authorize the high seas seizure of stateless vessels, which left the Council of the European Union reliant on existing enforcement powers in the law of the sea. Yet neither customary international law nor UNCLOS provide enforcement jurisdiction over stateless vessels, and the existence of seizure powers in the Migrant Smuggling Protocol remains debateable. While the drafting history of the Migrant Smuggling Protocol does not reveal an intention on behalf of the drafters to provide new jurisdictional powers beyond UNCLOS, this article has argued that the ambiguity of Article 8(7) left space for Western destination states to modify the meaning of ‘appropriate measures’ through state practice.

New maritime threats require flexible interpretation of the law of the sea. ¹⁵¹ UNCLOS provides the legal framework for combatting illicit activities at sea, but the legal rules contained therein do not provide comprehensive enforcement powers against all forms of transnational organized crimes committed at sea. Thus, some level of ambiguity, both in customary rules and treaty drafting, allows for international law to adapt to a constantly changing international environment, whether technological innovations, new social or political norms, or security threats. In the context of migrant smuggling, the EU legislator has repeatedly claimed that the Migrant Smuggling Protocol authorizes high seas enforcement actions against stateless smuggling vessels, and substantiated such claims through enforcement action, law reform and inter-state agreements. ¹⁵² Arguably, however, it was only the actions surrounding recent EUNAVFOR MED anti-smuggling mission, Operation Sophia, that finally crystalized the meaning of the term ‘appropriate measures’ as entailing seizure and arrest.

Yet the extraterritorial expansion of coercive state power is not without risks, even when done to combat transnational maritime crime. Over the last twenty years, Western destination states have positioned irregular migration by sea as a security threat in order to justify greater maritime enforcement powers, and relied on this logic of securitization to avoid human rights and refugee protections for boat migrants. ¹⁵³ While Operation Sofia closed down in 2020, EU member states, as well as other Western destination states world-wide, continue to take or facilitate coercive actions against migrants and asylum seekers on the high seas. These ongoing practices highlight the urgent need to clarify the scope of the term ‘appropriate measures’ in Article 8(7) of the Migrant Smuggling Protocol and to strengthen human rights and asylum protections for people escaping poverty, conflict, and persecution by sea.