At the end of 2024, a Chinese-flagged bulk carrier ship, Yi Peng 3, was at the centre of a diplomatic stand-off between China and a quartet of Baltic states. For several weeks between November and December, the Yi Peng 3 had lain in the Kattegat strait between Denmark and Sweden, surrounded by Danish, German and Swedish coastguard boats. They were awaiting China’s permission to send prosecutors and police on board the Yi Peng 3 to look for evidence that it had severed two fibreoptic data cables on the Baltic seabed a few days earlier. Two days after leaving a Russian port, the ship had apparently dragged its anchor along the seabed for more than 100 nautical miles (185 kilometres) in the area of the cables, one linking Finland and Germany, the other linking Lithuania and Sweden. It was even thought to have illegally turned off the on-board transponder broadcasting identification and tracking data for a few hours.
Despite the strong circumstantial evidence and suspicions that it was a deliberate act of sabotage potentially involving Russian agencies (which Russia denied), and despite the fact that it happened within Sweden’s exclusive economic zone (EEZ), neither Sweden nor any of the other affected countries had a legal right to board the Yi Peng 3 to look for evidence without China’s permission. By the time the Yi Peng 3 left the Kattegat on 21 December, Swedish authorities had only been allowed on board to observe a Chinese-led inspection.
The case of the Yi Peng 3 illustrates both the growing problem of damage to undersea cables and pipelines, and the difficulties countries face in combating it. In this Q&A, law of the sea expert Dr Pierre Thévenin explains some of the legal obstacles to investigating and prosecuting vessels suspected of damaging submarine cables and how European states could remove these obstacles with new legislation.
Q: How serious is the problem of damage to submarine cables today?
PT: Globally, there are around 200 repairs carried out on submarine cables every year, and this number has been relatively stable for more than a decade, according to the International Cable Protection Committee’s statistics. Around 86 per cent of these repairs are due to damage caused by anchoring or fishing accidents.
In the Baltic Sea, however, the problem has significantly increased since 2023. Between October 2023 and 25 December 2024, submarine telecommunication data cables were cut nine times, along with a gas pipeline and an underwater power cable between Estonia and Finland, called ESTLINK 2. In one of these incidents, another power cable, another gas pipeline and several other data cables may well have been damaged if the Finnish Navy and coastguard had not intercepted the tanker Eagle S, which some also suspect is part of Russia’s ‘shadow fleet’. In every case, the ships involved seem to have deliberately dragged their anchors along the seabed for long distances.
For the Baltic Sea, this issue is particularly concerning, not least because states in this region rely on submarine cables to ensure that electricity can be transferred across the Baltic Sea to offset volatility in local electricity markets. Furthermore, submarine telecommunication cables are vital to connectivity in the region, helping to ensure fast and reliable transfer of data.
Given the critical nature of this infrastructure and suspicions that it is being targeted by deliberate sabotage, in January 2025 NATO launched a joint naval operation called Baltic Sentry. Its stated aim is to ‘deter any future attempts by a state or non-state actor to damage critical undersea infrastructure’ in the Baltic.
In June this year I had a chance to speak to Squadron Vice-Admiral Jean-François Quérat, the Commander of the Atlantic maritime theatre for the French Navy, who was in Malmö, Sweden, to discuss the main security challenges facing the Baltic Sea and the Arctic Ocean and to strengthen Franco–Swedish cooperation. The bulk of our exchange was focused on the protection of submarine cables and the issue of the Russian shadow fleet. As Admiral Quérat underlined, these are threats the French Navy is increasingly concerned about, and France was one of the first states to join Baltic Sentry. A lot of my own current research is focused on the legal aspects of prosecuting damage to submarine cables.
Q: In most of the recent cases of damage to submarine cables in the Baltic, it seems to have been relatively clear which ships were involved. Why has it proved so difficult to prosecute these cases?
PT: The technical identification of ships involved in such cases is becoming easier and easier. All vessels over a certain size are legally obliged to send a constant stream of data about their exact position, speed and more via the Automatic Identification System (AIS). Thus, detailed information about ships’ movements is readily available on tracking websites such as Marine Traffic. Several firms, especially in the European Union (EU) and New Zealand, have developed tools using artificial intelligence to analyse large amounts of this data to detect vessels with suspicious behaviour, such as deviating from traditional shipping lanes or travelling unusually slowly. Admiral Quérat also told me that France is enhancing its capabilities to surveil the deep seabed.
However, while we may know for certain which ships are involved, there are several legal obstacles to investigating these cases, even when they happen within a coastal state’s EEZ—which is a maritime zone outside a state’s territorial waters extending up to 200 nautical miles (370 km) from the state’s coastal baselines.
Probably the biggest of these obstacles is that, as it is currently interpreted, the 1982 United Nations Convention on the Law of the Sea (UNCLOS) does not automatically give a coastal state the authority to board and search a foreign vessel suspected of damaging submarine cables in the state’s EEZ. That can only be done with the cooperation of the ship’s flag state—meaning the state where it is legally registered. As we saw in the case of the Yi Peng 3, this permission can be very slow to come, if it comes at all, by which time the ship may be far outside the coastal state’s jurisdiction and the reach of its coastguard vessels.
Q: Is there a way around the need to obtain the flag state’s permission?
PT: Yes, I believe that states can construct a sound legal argument for boarding ships suspected of damaging undersea cables that land on their territory, regardless of whether the relevant flag state grants prior permission.
UNCLOS is a framework convention, which means that states have some latitude in how they implement its provisions. When it comes to EEZs, states are allowed to establish laws to regulate, within reason, what other states’ ships can and cannot do within these zones to safeguard their sovereign rights. For instance, states are free to decide how they want to regulate marine research, fishing and mineral exploitation in their EEZs.
This latitude can also be used to protect submarine cables. Under Article 56(1)(a) of UNCLOS, coastal states have the right of economic exploitation and exploration in their EEZs, from the seabed upwards. Laying and using cables could be considered economic exploitation. The only threshold to be met is that the activity has an economic interest for the coastal state, which submarine cables carrying either electricity or data do. For instance, in addition to the initial repair costs, the damage to ESTLINK 2 led to an electricity price hike on the Estonian market, causing consumers to pay more for their electricity.
Article 60 of UNCLOS allows coastal states to establish safety zones in their EEZs around ‘installations and structures for the purposes provided for in Article 56’. Within these zones—which must be well publicized—coastal states ‘may take appropriate measures to ensure the safety’ of the installation, including setting rules for what ships can and cannot do there. If a ship breaches these rules within the safety zone, the coastal state can claim the authority to board and inspect the ship without the flag state’s prior permission.
The term ‘installations’ has been left undefined in the Convention, giving states the opportunity to define its meaning through their own practice. I can see nothing in the drafting history of UNCLOS to suggest that undersea cables that land on a coastal state’s territory could not be considered as installations under Article 60.
The only thing coastal states in the Baltic would need to do, then, is to adopt legislation establishing these safety zones and the rules that apply within them. In fact, Denmark has already done so.
To minimize impacts on freedom of navigation—a high priority for the EU and NATO members—I do not think this legislation should prohibit all navigation within the safety zones. Rather, I agree with the law of the sea expert Alexander Lott and others that coastal states should only prohibit activities that can interfere with the seabed, like bottom trawling, dredging and anchoring. This would be in line with the spirit of UNCLOS, especially Article 56(2), which says that, in exercising its own rights with the EEZ, the coastal state should have due regard for the rights and duties of other states.
Q: Do you think this kind of approach could work in practice?
PT: Certainly. Australia, Denmark and New Zealand have all passed laws on protecting submarine cables in their EEZs, including establishing safety zones. If all of the Baltic Sea coastal states established similar laws, this would mean uniform protection for submarine cables in the whole Baltic Sea—all of which is within the territorial seas or EEZs of the various coastal states.
However, there is another step that states can take to make these laws more effective in practice. Admiral Quérat pointed out that the cost and workload associated with prosecuting suspected vessels need to be minimized in order to facilitate enforcement. To do this, states could apply the ‘strict liability’ standard for breaching the rules of the safety zone. This means the prosecution would not have to prove fault or intent, only that the infraction took place, in order for the master of the vessel to be held liable. The only exception would be cases of force majeure, when the breach was unavoidable or was done to avoid imminent danger.
I would also recommend that states reverse the burden of proof, so that when law-enforcement authorities observe a breach of the rules in a safety zone, it would be up to the master of the vessel to prove their innocence, not the prosecutor to prove fault.
All of what I suggest and argue for is in line with UNCLOS. I believe that if the Baltic states were to adopt such laws, it could greatly reduce the risk of damage to vital communications and power infrastructure—whether that damage is accidental or a deliberate tactic of hybrid warfare.
ABOUT THE AUTHOR(S)
Dr Pierre Thévenin is a Researcher with SIPRI’s European Security Programme and an international technical expert for Expertise France.
At the end of 2024, a Chinese-flagged bulk carrier ship, Yi Peng 3, was at the centre of a diplomatic stand-off between China and a quartet of Baltic states. For several weeks between November and December, the Yi Peng 3 had lain in the Kattegat strait between Denmark and Sweden, surrounded by Danish, German and Swedish coastguard boats. They were awaiting China’s permission to send prosecutors and police on board the Yi Peng 3 to look for evidence that it had severed two fibreoptic data cables on the Baltic seabed a few days earlier. Two days after leaving a Russian port, the ship had apparently dragged its anchor along the seabed for more than 100 nautical miles (185 kilometres) in the area of the cables, one linking Finland and Germany, the other linking Lithuania and Sweden. It was even thought to have illegally turned off the on-board transponder broadcasting identification and tracking data for a few hours.
Despite the strong circumstantial evidence and suspicions that it was a deliberate act of sabotage potentially involving Russian agencies (which Russia denied), and despite the fact that it happened within Sweden’s exclusive economic zone (EEZ), neither Sweden nor any of the other affected countries had a legal right to board the Yi Peng 3 to look for evidence without China’s permission. By the time the Yi Peng 3 left the Kattegat on 21 December, Swedish authorities had only been allowed on board to observe a Chinese-led inspection.
The case of the Yi Peng 3 illustrates both the growing problem of damage to undersea cables and pipelines, and the difficulties countries face in combating it. In this Q&A, law of the sea expert Dr Pierre Thévenin explains some of the legal obstacles to investigating and prosecuting vessels suspected of damaging submarine cables and how European states could remove these obstacles with new legislation.
Q: How serious is the problem of damage to submarine cables today?
PT: Globally, there are around 200 repairs carried out on submarine cables every year, and this number has been relatively stable for more than a decade, according to the International Cable Protection Committee’s statistics. Around 86 per cent of these repairs are due to damage caused by anchoring or fishing accidents.
In the Baltic Sea, however, the problem has significantly increased since 2023. Between October 2023 and 25 December 2024, submarine telecommunication data cables were cut nine times, along with a gas pipeline and an underwater power cable between Estonia and Finland, called ESTLINK 2. In one of these incidents, another power cable, another gas pipeline and several other data cables may well have been damaged if the Finnish Navy and coastguard had not intercepted the tanker Eagle S, which some also suspect is part of Russia’s ‘shadow fleet’. In every case, the ships involved seem to have deliberately dragged their anchors along the seabed for long distances.
For the Baltic Sea, this issue is particularly concerning, not least because states in this region rely on submarine cables to ensure that electricity can be transferred across the Baltic Sea to offset volatility in local electricity markets. Furthermore, submarine telecommunication cables are vital to connectivity in the region, helping to ensure fast and reliable transfer of data.
Given the critical nature of this infrastructure and suspicions that it is being targeted by deliberate sabotage, in January 2025 NATO launched a joint naval operation called Baltic Sentry. Its stated aim is to ‘deter any future attempts by a state or non-state actor to damage critical undersea infrastructure’ in the Baltic.
In June this year I had a chance to speak to Squadron Vice-Admiral Jean-François Quérat, the Commander of the Atlantic maritime theatre for the French Navy, who was in Malmö, Sweden, to discuss the main security challenges facing the Baltic Sea and the Arctic Ocean and to strengthen Franco–Swedish cooperation. The bulk of our exchange was focused on the protection of submarine cables and the issue of the Russian shadow fleet. As Admiral Quérat underlined, these are threats the French Navy is increasingly concerned about, and France was one of the first states to join Baltic Sentry. A lot of my own current research is focused on the legal aspects of prosecuting damage to submarine cables.
Q: In most of the recent cases of damage to submarine cables in the Baltic, it seems to have been relatively clear which ships were involved. Why has it proved so difficult to prosecute these cases?
PT: The technical identification of ships involved in such cases is becoming easier and easier. All vessels over a certain size are legally obliged to send a constant stream of data about their exact position, speed and more via the Automatic Identification System (AIS). Thus, detailed information about ships’ movements is readily available on tracking websites such as Marine Traffic. Several firms, especially in the European Union (EU) and New Zealand, have developed tools using artificial intelligence to analyse large amounts of this data to detect vessels with suspicious behaviour, such as deviating from traditional shipping lanes or travelling unusually slowly. Admiral Quérat also told me that France is enhancing its capabilities to surveil the deep seabed.
However, while we may know for certain which ships are involved, there are several legal obstacles to investigating these cases, even when they happen within a coastal state’s EEZ—which is a maritime zone outside a state’s territorial waters extending up to 200 nautical miles (370 km) from the state’s coastal baselines.
Probably the biggest of these obstacles is that, as it is currently interpreted, the 1982 United Nations Convention on the Law of the Sea (UNCLOS) does not automatically give a coastal state the authority to board and search a foreign vessel suspected of damaging submarine cables in the state’s EEZ. That can only be done with the cooperation of the ship’s flag state—meaning the state where it is legally registered. As we saw in the case of the Yi Peng 3, this permission can be very slow to come, if it comes at all, by which time the ship may be far outside the coastal state’s jurisdiction and the reach of its coastguard vessels.
Q: Is there a way around the need to obtain the flag state’s permission?
PT: Yes, I believe that states can construct a sound legal argument for boarding ships suspected of damaging undersea cables that land on their territory, regardless of whether the relevant flag state grants prior permission.
UNCLOS is a framework convention, which means that states have some latitude in how they implement its provisions. When it comes to EEZs, states are allowed to establish laws to regulate, within reason, what other states’ ships can and cannot do within these zones to safeguard their sovereign rights. For instance, states are free to decide how they want to regulate marine research, fishing and mineral exploitation in their EEZs.
This latitude can also be used to protect submarine cables. Under Article 56(1)(a) of UNCLOS, coastal states have the right of economic exploitation and exploration in their EEZs, from the seabed upwards. Laying and using cables could be considered economic exploitation. The only threshold to be met is that the activity has an economic interest for the coastal state, which submarine cables carrying either electricity or data do. For instance, in addition to the initial repair costs, the damage to ESTLINK 2 led to an electricity price hike on the Estonian market, causing consumers to pay more for their electricity.
Article 60 of UNCLOS allows coastal states to establish safety zones in their EEZs around ‘installations and structures for the purposes provided for in Article 56’. Within these zones—which must be well publicized—coastal states ‘may take appropriate measures to ensure the safety’ of the installation, including setting rules for what ships can and cannot do there. If a ship breaches these rules within the safety zone, the coastal state can claim the authority to board and inspect the ship without the flag state’s prior permission.
The term ‘installations’ has been left undefined in the Convention, giving states the opportunity to define its meaning through their own practice. I can see nothing in the drafting history of UNCLOS to suggest that undersea cables that land on a coastal state’s territory could not be considered as installations under Article 60.
The only thing coastal states in the Baltic would need to do, then, is to adopt legislation establishing these safety zones and the rules that apply within them. In fact, Denmark has already done so.
To minimize impacts on freedom of navigation—a high priority for the EU and NATO members—I do not think this legislation should prohibit all navigation within the safety zones. Rather, I agree with the law of the sea expert Alexander Lott and others that coastal states should only prohibit activities that can interfere with the seabed, like bottom trawling, dredging and anchoring. This would be in line with the spirit of UNCLOS, especially Article 56(2), which says that, in exercising its own rights with the EEZ, the coastal state should have due regard for the rights and duties of other states.
Q: Do you think this kind of approach could work in practice?
PT: Certainly. Australia, Denmark and New Zealand have all passed laws on protecting submarine cables in their EEZs, including establishing safety zones. If all of the Baltic Sea coastal states established similar laws, this would mean uniform protection for submarine cables in the whole Baltic Sea—all of which is within the territorial seas or EEZs of the various coastal states.
However, there is another step that states can take to make these laws more effective in practice. Admiral Quérat pointed out that the cost and workload associated with prosecuting suspected vessels need to be minimized in order to facilitate enforcement. To do this, states could apply the ‘strict liability’ standard for breaching the rules of the safety zone. This means the prosecution would not have to prove fault or intent, only that the infraction took place, in order for the master of the vessel to be held liable. The only exception would be cases of force majeure, when the breach was unavoidable or was done to avoid imminent danger.
I would also recommend that states reverse the burden of proof, so that when law-enforcement authorities observe a breach of the rules in a safety zone, it would be up to the master of the vessel to prove their innocence, not the prosecutor to prove fault.
All of what I suggest and argue for is in line with UNCLOS. I believe that if the Baltic states were to adopt such laws, it could greatly reduce the risk of damage to vital communications and power infrastructure—whether that damage is accidental or a deliberate tactic of hybrid warfare.
ABOUT THE AUTHOR(S)