Are sabotage of submarine pipelines an ‘armed attack’ triggering a right to self-defence?

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On 26 and 27 September 2022, explosions damaged NordStream 1 and NordStream 2 pipelines in the Baltic Sea (here). These are major transboundary pipelines (consisting of two pipelines each) transporting gas from Russia to Germany. They cross the territorial sea of three States (Russia, Denmark and Germany) and the exclusive economic zone (‘EEZ’) of five States (Russia, Finland, Sweden, Denmark and Germany). Nord Stream 1 is owned and operated by NordStream AG. NordStream 2 is owned and operated by NordStream 2 AG. Both companies are incorporated in Switzerland.

NordStream AG announced that the damages on NordStream 1 took place in the EEZ of Denmark and/or Sweden (here). No State or non-State actor has claimed responsibility for the explosions, and it is unclear whether the damages can be attributed to a particular State, despite the fact that different sources have pointed the finger to specific States (here and here).

Here, we are not concerned with whether the explosion is attributed to any particular State (or non-State actor). This incident contextualizes the security concerns that States have about critical submarine infrastructure, such as pipelines and cables, and we discuss the legal questions that the incidents give rise to.

Pipelines are essential for ensuring energy security; cables are vital for both energy security and the security of telecommunications. All these concerns have been essential in the priority of States for years. An earlier incident in the same region against the fiber cable between Norway’s mainland and the archipelago of Svalbard demonstrated the vulnerability of such offshore infrastructure and the difficulties in finding links to particular individuals or States. But, since the NordStream explosions, and against the background of an energy crisis in Europe, these concerns have ‘sky-rocketed’ not only in Northern Europe but also in South Europe, and beyond (here and here).

The explosions have been described ‘acts of sabotage’ (here), which may be criminal acts under some domestic laws. But, the sabotage of pipelines/cables as such is not specifically prohibited under the law of the sea – albeit other rules of international law, including obligations to preserve and protect the marine environment, may be violated by such conduct.

International press recorded concerns regarding jus ad bellum. The Editorial Board of the Washington Post stated that because “the explosions took place in international waters”, “they cannot be construed as a direct attack on any NATO member, which could have triggered the alliance’s mutual-defense agreement.” Although this statement concerns exclusively the scope of the NATO Treaty, it raises questions about whether an attack against offshore pipelines and cables can give rise to an ‘armed attack’ against a particular State, which under customary international law and the UN Charter entitles the victim State to exercise its right to self-defence.

The ILA Committee on Submarine Cables and Pipelines is currently working on aspects of the above issues (see First and Second Report), and is likely to produce a set of guidelines on these matters in the following year(s). As a caveat, one of the co-authors of this post is co-Rapporteur of this ILA Committee, but the views in this essay do not reflect nor preempt the Committee’s views on the matters discussed below. 

Below, we sketch out some arguments and challenges about whether sabotaging transboundary submarine pipelines, such as NordStream, can constitute an ‘armed attack’ against a particular State or States triggering the UN Charter article 51 and customary right to self-defense.

Burden of Proof

A main difficulty in situations such as the damage on the NordStream pipelines, is that the State invoking the right to self-defence bears the burden of proving the facts showing the existence of such an attack against it by a particular State (International Court of Justice (‘ICJ’), Oil Platforms (2003), [51]). In this connection, generic announcements that an attack or other incident will take place prior to the explosions are insufficient evidence to support that any subsequent attack is the work of the State making such public statements (Oil Platforms, [60]).

An ‘Armed Attack’ against Whom?

According to the ICJ in Military and Paramilitary Activities in and Against Nicaragua (1986) [191], as well as in Oil Platforms [51], an ‘armed attack’ involves ‘the most grave forms of the use of force’. ‘Other less grave forms’ of use of force do not meet this threshold. In Nicaragua, the Court had considered the distinction between an ‘armed attack’ and mere ‘frontier incidents’, and relied on the following criteria to draw this distinction: the ‘scale and effects’ of the attack [195], and the ‘circumstances and motivations’ of the attack [231]. The ‘scale and effects’ criterion is particularly relevant for assessing whether blowing-up major transboundary pipelines may constitute an ‘armed attack’.

In Oil Platforms, the Court was concerned with use of force against fixed infrastructure (platforms) in the Persian Gulf, but not about whether these instances constituted an ‘armed attack’ against Iran. The United States (‘US’) never denied that its actions against the Iranian platform amounted to the use of armed force.  

Instead, the issue of armed attack arose in relation to the US’ argument that targeting US-flagged or US military vessels constituted ‘armed attack’ by Iran against the US thus entitling the US to use force in self-defence; and that it was on this basis that the US used force lawfully against Iranian platforms in the Persian Gulf, thus meeting the essential security interests’ exception of the bilateral 1955 Treaty of Amity.

The Court expressly did ‘not exclude the possibility that the mining of a single military vessel might suffice’ to bring into play the right of self-defence (Oil Platforms, [72 (emphasis added)]).

However, in relation to non-military vessels, the US had argued that the hitting with a missile of a US-flagged vessel (Sea Isle City) was the last of a series of missile attacks against US-flagged vessels in Kuwaiti waters (including the mining of the US-flagged Bridgeton and of the US-owned Texaco Caribbean, the firing on US navy helicopters and the minelaying by an Iranian vessel, the Iran Ajr [50], [62]). The Court found that ‘even taken cumulatively’, these incidents did not constitute an armed attack on the US qualifying as a ‘most grave’ form of use of force [64].  In relation to the strike of Sea Isle City, the Court considered that a missile allegedly fired from Iran ‘could not have been aimed at the specific vessel, but simply programmed to hit some target in Kuwaiti waters.’ [64] It further considered that it had not been established that the mine struck by the Bridgeton was laid with the specific intention of harming that ship, or other US vessels. [64]

The Court’s reasoning suggests: first, that it is not excluded that damaging commercial vessels carrying the flag of a State could constitute an armed attack against the flag State if it is established that the vessels were the intended target of the attack; second, assuming that the Court’s reasoning in paragraph [64] is better understood as dealing with cumulative ‘less grave forms of use of force’, such instances might meet the threshold of an ‘armed attack’ (see also Armed Activities (DRC v Uganda) (2005) [146].

However, whether attacks on pipelines on the continental shelf and the EEZ as well as on the high seas, would constitute ‘the most grave form’ of use of force qualifying as an ‘armed attack’ against a particular State (or States) is not straightforward.

Although a quantitative (‘scale’) and qualitative (‘effects’) argument could be made, they face significant limitations. The following discussion takes the NordStream incident as context.

First, the attacks against three pipelines of Nord Stream 1 and 2 either taken individually or cumulatively within less than two days might reach the threshold of gravity considering that all three pipelines were specifically targeted, as the Court reasoned in Oil Platforms. Yet, in that case, the Court was dealing with vessels that carried the flag of the State which claimed to be the victim of the alleged armed attack.

In relation to transboundary offshore pipelines, the main challenge is that it is unclear against which State an alleged ‘armed attack’ takes place.

If the damage to a pipeline or cable occurs in the internal waters or territorial sea of a coastal State, the attack would be against that coastal State’s territorial integrity, because the coastal State exercises sovereignty in these zones, arguably giving rise to its right of self-defence.

In relation to a pipeline or cable used entirely for military purposes, it may be argued that the State whose military owns, operates and uses the pipeline or cable would be the victim State entitled to self-defence irrespective of where the pipeline lies (depending on its location there could be concurrent individual rights of self-defence). For instance, if a ‘military pipeline’ is attacked in the internal waters or the territorial sea of another State, that coastal State may also be entitled to self-defence.

But, on the CS and in the EEZ, as is the case of the NordStream incident, coastal States enjoy and exercise only sovereign rights exclusively on the grounds provided by international law, while there is freedom of laying pipelines and cables, subject to treaty or customary rules concerning the coastal State’s CS rights. While the coastal State has exclusive jurisdiction over ‘artificial islands, installations and platforms’ in its EEZ and CS (LOSC Articles 60 and 80), as well as jurisdiction over cables and pipelines constructed or used in connection with the exploration of its CS or exploitation of its resources or the operations of artificial islands, installations and structures under its jurisdiction (LOSC Article 79(4)), pipelines and cables unconnected to the latter are not subject to the general jurisdiction of the coastal State, except in relation to ‘reasonable measures for the exploration of the continental shelf, the exploitation of its natural resources and the prevention, reduction and control of pollution from pipelines’ (LOSC Article 79(2)). In light of the limited jurisdiction that coastal States have in the CS and the EEZ, whether an ‘armed attack’ against the such State took place by targeting a commercial pipeline located in its CS/EEZ is highly debatable.

Separately, although pipelines do not have flags, like vessels, they are owned and operated by companies incorporated in some State jurisdiction. The question arises whether States in whose jurisdiction the company that owns and/operates the pipeline are incorporated may be the victim of an ‘armed attack’ against the pipeline, giving rise to its right to self-defence. In the case of NordStream, this would be Switzerland. At the time of writing this essay, we are not aware of any State practice that would support the proposition that the State of incorporation of the pipeline company would be a victim of an ‘armed attack’ of a pipeline in the maritime zone within or outside a State’s jurisdiction. Nor has Switzerland made a relevant claim to the right of self-defence for the particular incident.

Second, it could be argued that the explosions of NordStream 1 and 2 have unprecedented impact on the energy security of supply of multiple importing States in Europe and the security of demand of the exporting State, on the functioning of a whole regional gas market, and even on the capacity of numerous importing European States to comply with some human rights obligations vis-à-vis individuals in their territory, because they rely on energy access through NordStream in order to ensure that populations in their territories have access to energy and thus to enjoy their right to health. In the present instance, the fact that at the time of the explosions there had been no ongoing gas exports from Russia through these pipelines would lessen the strength of such a qualitative argument. However, in any event, an important challenge in relation to such an argument is that the effects on a State’s economy is not an established criterion for assessing whether instances of use of force reach the level of gravity required for an ‘armed attack’ against the State whose economy is affected.

Necessity and proportionality of self-defence

Even assuming that the sabotage on offshore pipelines and cables could constitute an ‘armed attack’ against a particular State, any response in self-defence would have to meet the requirements of necessity and proportionality under jus ad bellum (ICJ Legality of the Threat or Use of Nuclear Weapons, [41]; Military and Paramilitary Activities in and Against Nicaragua (1986) [176]; Oil Platforms [76]).

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Paula Silfverstolpe says

October 24, 2022

Thank you for a very interesting post!

Another interesting question is whether NATO article 5 would cover such situations if they were to be considered "armed attacks" for the purpose of article 51 of the UN Charter. The answer can be found in article 6 of the NATO treaty which limits the application of article 5 to armed attacks on member states territories as well as forces, vessels and aircrafts with some geographical limitations. It doesn't seem therefore that article 5 of the NATO Treaty has any relevance in case of armed attacks on member states undersea cables, pipelines or any other offshore installations located outside the territorial sea (e.g EEZ, continental Shelf). By contrast, the EU Lisbon Treaty article 42 ("mutual defense clause") only applies to member states "territories" (and not to other assets abroad) going by the language of the article. However, article 222 ("solidarity clause") of the Lisbon Treaty, for cases of “terrorism” and “man-made disasters”, appears to apply outside the member states territory pursuant to Decision 2014/415/which defines a member state’s territory for these purposes to include not only its land area, internal waters, territorial sea, and airspace, but also infrastructure, such as offshore oil and gas installations, located in its territorial sea, exclusive economic zone, or continental shelf.

Paula Silfverstolpe