Submarine cables and pipelines are vitally important for energy supply, global communications and economic activity. But several recent high-profile incidents have exposed their vulnerability to deliberate damage from state and non-state actors. In April 2021, Norway reported that several kilometres of its fibreoptic cables disappeared from the Svalbard archipelago, leaving Norway unable to monitor submarine activity in the region. These cables formed part of an extensive network of high-tech cables and sensors used for scientific research and maritime surveillance. Better known, on 26 September 2022, a series of explosions damaged the Nord Stream 1 and 2 gas pipelines in the Baltic Sea, which were built to transport gas from Russia to Germany. While suspicions initially fell on Russia, Dutch intelligence suggest that the explosion was caused by experienced divers belonging to a ‘pro-Ukrainian group’.
One year later, damage to the Balticconnector gas pipelines and nearby cables heightened fears among Baltic and Nordic states about the vulnerability of their critical submarine infrastructure to deliberate damage. These fears were exacerbated by the severance of two more cables – one between Finland and Germany and the other between Sweden and Lithuania – in mid-November 2024. In both cases, affected governments raised concerns about malicious damage, with commentators drawing a bridge to suspected Russian hybrid warfare. However, in both cases, suspicion ultimately fell on Chinese registered vessels (here and here). Despite initial concerns about sabotage, police and navy authorities have been cautious in confirming whether the incidents were intentional or accidental. Despite this, many states remain worried about the security of their offshore and submarine infrastructure. In November 2024, for example, Sweden scuppered plans to build 13 offshore windfarms in the Baltic Sea, citing defence concerns.
Despite this, international law does not provide states with adequate enforcement powers to prevent or combat sabotage of submarine cables and pipelines by state and non-state actors beyond their territorial seas. On the high seas and EEZ, only flagships may stop, board, search and arrest vessels suspected of sabotage. This has left concerned states focused on monitoring and deterrence patrolling of critical submarine infrastructure. Several previous posts have examined whether sabotage against critical submarine infrastructure outside the territorial waters of a coastal state can amount to an armed attack, triggering the right of self-defence under Article 51 of the UN Charter (see here and here). While an important question, this post instead explains what actions states could take to expand their enforcement powers under the law of the sea.
Closing the Enforcement Gap: Three Proposals
International law and domestic practice provide states with several possible models for expanding their extraterritorial enforcement jurisdiction to prevent and combat high-seas sabotage of submarine cables and pipelines.
UNSC Resolution
Given fears of hybrid warfare, the UNSC could authorize states to use force at sea to combat high seas/EEZ sabotage of submarine cables and pipelines under Article 42 of the UN Charter, like Resolution 1816 (2008) on piracy and Resolution 2240 (2015) on migrant smuggling. In 2008, the Security Council authorized states that were cooperating with the transitional government of Somalia to enter Somalian territorial waters for the purpose of repressing acts of piracy and armed robbery at sea off the Somalian coast. More relevantly, in 2015, the Security Council authorized states to inspect vessels on the high seas suspected of being used to smuggle migrants from Libya to Europe, provided that ‘good faith efforts’ to obtain the consent of the vessel’s flag state had been made. Res 2240 additionally authorized states to take ‘further action’ with regard to vessels confirmed to be engaged in migrant smuggling.
Like Res 2240, the Security Council could authorize affected coastal states to stop, board and search foreign vessels suspected of being engaged in sabotage to submarine cables and pipelines, provided that the boarding state has first made good faith efforts to obtain authorization from the flag state. The resolution could further authorize coastal state warships to seize inspected vessels confirmed to be engaged in sabotage and escort such vessels to the nearest designated port for further investigation. However, at this point in time, a UNSC resolution is unlikely. China and Russia have been reluctant to support resolutions authorizing broadly applicable enforcement powers. Given this, both Res 1816 and Res 2240 were justified by reference to the risks to international peace and security caused by regional conflicts in Somalia and Libya. And given the recent accusations of Chinese and Russian (here and here) involvement in sabotage, this reluctance will likely be reinforced.
Cable and Pipeline Protection Zones
Over the last few years, several states have established submarine cable protection zones. Japan and Singapore have each established submarine cable corridors around designated cables, which prohibit or restrict certain activities, such as fishing, anchoring and dredging in the declared areas. Australia and New Zealand have also established cable protection zones, which are enforced by sea and air patrols. The International Cable Protection Committee has described the Australian scheme as ‘world best practice’. Consistently with UNCLOS, other states could establish protection zones modelled upon the Australian scheme.
Under the Australian Scheme, the Australian Communications and Media Authority (ACMA) can declare a cable protection zone within Australia’s territorial waters and EEZ up to 3.7km wide and 2000m deep. The ACMA can declare a cable protection zone around an existing cable of national significance, or submarine cable operators can request the ACMA to declare a protection zone. The legislative scheme also allows the Australian Government to recover the cost of the protection scheme from the telecommunications industry. Once a cable zone is declared, certain laws prohibit or restrict activities in that zone that are likely to damage submarine cables, such as dredging and fishing. Severe criminal penalties apply to Australian nationals or Australian registered ships engaged in the prohibited or restricted conduct also apply. While under international law, states may criminalize sabotage involving a foreign national or ship, they can only enforce these laws against their own national vessels or against foreign individuals subsequently entering their territory.
International Convention for the Suppression of Unlawful Acts against Submarine Cables and Pipelines
To fill this gap, states could develop an international convention for the suppression of sabotage of submarine cables and pipelines. International law provides various models to expand state rights and responsibilities at sea.
Firstly, the treaty should contain a general obligation on states not to engage in acts that constitute intentional damage to submarine cables and pipelines. This obligation extends to state parties acting outside their own territorial waters. Breach of this obligation gives rise to state responsibility and, when coupled with a dispute resolution clause, would give affected states an avenue to litigate alleged breaches before the ICJ. Alongside this obligation, a future treaty should oblige state parties to take specific measures to prevent sabotage to submarine cables and pipelines, including the adoption of laws and regulations; training of law enforcement and military personnel; the establishment of submarine cables and pipeline protection zones; deterrence patrolling; and the provision of training and technical assistance to other states parties.
Additionally, a treaty needs strong anti-impunity obligations to deter sabotage by non-state actors. To facilitate domestic implementation, the treaty should replicate the criminal offence in Article 113 of UNCLOS but extend criminalization to cables and pipelines below territorial seas and landing sites. To prevent safe havens, the treaty should additionally oblige all state parties to establish universal prescriptive jurisdiction over the treaty offences, which is permitted under international law. This should be coupled with an obligation to prosecute or extradite alleged offenders who are found within a state party’s territory.
Most importantly, a future treaty should grant affected coastal states the power to interdict foreign vessels suspected of sabotaging submarine cables and pipelines beneath the high seas/EEZ. Modelled upon Articles 109 and 110 of UNCLOS for unauthorized high seas radio broadcasting, the treaty should grant the coastal state in whose territory the sabotaged cable or pipeline lands the right to stop, board and search suspect vessels and, in cases where suspicions prove justified, the right to take further enforcement measures against the vessel and persons and cargo on board. While the treaty cannot authorize boarding states to take enforcement action against foreign government vessels, these extended powers will hopefully deter states from using private and merchant vessels for sabotage.
At this point, there is no international intergovernmental organization responsible for submarine cables and pipelines. This leaves states without a UN body with a mandate to promote treaty negotiations. Nevertheless, several possibilities exist. The IMO could develop a resolution on ‘measures to prevent unlawful acts against submarine cables and pipelines involving ships’, to the extend that such measures fall within its mandate. This resolution could lay the foundation for a future convention. Alternatively, the ILC could appoint a special rapporteur to develop a set of draft articles, as a basis for treaty negotiations before the Sixth Committee. Finally, concerned states could formally request the UNGA to mandate treaty negotiations for a specialized convention. Like the process for the 2017 Treaty on the Prohibition of Nuclear Weapons, concerned states could sponsor a series of international conferences on the topic, including states, civil society and other stakeholders. This would help build momentum for treaty negotiations.
