Attribution of Naval Mine Strikes in International Law

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On Thursday, June 13, two ships were damaged within forty-five minutes by (current evidence suggests) limpet mines, while transiting the Gulf of Oman at the mouth of the Strait of Hormuz. The Japanese product tanker, Kokuka Courageous sustained damage from either a limpet mine or a projectile, just as Prime Minister Shinzo Abe met with Iranian Supreme Leader Ayatollah Ali Khamenei in Tehran to try to reduce regional tensions. The Front Altair, also a tanker, suffered far more severe damage to its starboard hull, including a hole at the waterline, which – it has been suggested – was the result of a torpedo strike. This is very difficult to confirm – torpedoes tend to cause much more significant damage, and the damage sustained by Front Altair might also be consistent with a moored or floating mine strike, or the detonation of an attached limpet mine. Both ships caught fire and their crews abandoned ship. Four ships were also damaged by limpet mines off the coast of Fujairah on May 12, 2019. A UAE inquiry pinned responsibility on an ‘unidentified state actor.’

World oil prices increased as daily freight rates for oil supertankers climbed as much as fifty percent to reflect the heightened risk. Insurance rates for a seven-day transit have increased fifteen percent. Some seventy of the world’s supertankers are in the region – ten percent of global capacity – but many remain idle due to the threat. The United States blamed Iran for the attacks, and indeed there is evidence that points to Iranian involvement. The UK also attributes responsibility to Iran. Iran has denied responsibility, and Iranian Foreign Minister Javad Zarif responded on twitter that the United States or its allies were likely behind the assaults and that the charge was ‘[without] a shred of factual or circumstantial evidence.’

The United States has pledged to keep the Strait of Hormuz (SOH) open to traffic. Secretary of State Mike Pompeo attributed the attacks to Iran based upon ‘intelligence, the weapons used, the level of expertise needed to execute the operation, recent similar Iranian attacks on shipping, and the fact that no proxy group operating in the area has the resources and proficiency to act with such a high degree of sophistication.’ On June 17 he doubled down, promising to present in the coming days ‘lots of data, lots of evidence’ linking the attacks to Iran. President Trump stated flatly, ‘Iran did do it.’ U.S. Central Command released a video which appears to show an Iranian Revolutionary Guard Corp Navy (IRGCN) patrol boat removing an unexploded limpet mine from the Kokuka Courageous. Trump added, ‘I guess one of the mines didn’t explode and it’s probably got essentially Iran written all over it… It was them that did it.’

In this piece, we explore the available evidence for attribution in light of the international law on point. May the attacks be attributed to Iran, and if not, what additional evidence would have to be produced? And once (if) attribution of the attacks is made out, what measures may affected states then take in response? Since there is no evidence that there exists an international armed conflict under Common Article 2 of the Geneva Conventions, we do not address international humanitarian law, although in the last few days the shoot down of a US UAV and reports of a bombing mission switch off are starting to complicate this assessment.

The cases

Attributing responsibility for the attacks is informed by standards of international law. Once attribution is established, then injured states, such as Japan, are permitted to employ lawful countermeasures to prevent continuing wrongful acts and induce compliance by Iran of international law. The International Court of Justice has addressed these issues in three landmark cases, which focus (albeit to differing degrees) on attribution for mine strikes and lawful responses by injured states. The Corfu Channel Case, the Military and Paramilitary Activities Case, and the Oil Platforms Case each addressed naval mines, reaching somewhat idiosyncratic conclusions, especially about attribution. But taken as a whole body of law, they help to craft some conclusions on Iran’s legal responsibility and the rights of injured states to respond.

The Corfu Channel Case arose from a series of navigational incidents in 1946 in which British warships were damaged, and British sailors killed by sea mines laid by Albania. The incidents occurred while the warships were engaged in transit of the Corfu Channel, and in rescue operations after two units were severely damaged by mines in the channel, both within and outside the Albanian territorial sea. At its narrowest point, the channel was entirely within the abutting territorial seas of Albania and Greece. The Allies had swept the channel the year before, so the mines that struck the British warships in 1946 had been newly laid. The dispositive issue in the case was whether Albania had any responsibility relating to the mine strikes. Although Albania denied it laid the mines or even had the capability to do so, the Court concluded that regardless of who laid the mines Albania bore responsibility for ensuring safe transit its territorial sea. (In later decades, Albania admitted that it had laid the mines and paid reparations to the United Kingdom – see UK-Albanian Final Settlement MOU, in which Albania agreed to pay $2 million reparations, 63 BYIL 781 (1992). Payment was made in 1996). But the Court determined that Albania must have been aware of their being laid (regardless of which state actually laid them) given that they had permanently manned shore gun batteries and observation posts established along the channel:

From all the facts and observations mentioned above, the Court draws the conclusion that the laying of the minefield which caused the explosions on October 22nd, 1946, could not have been accomplished without the knowledge of the Albanian Government. (p22)

The 1949 decision ruled that Albania had an obligation to notify other states of the presence of the mines, and consequently bore responsibility for the damage inflicted upon the warships (and the deaths of the sailors).

In the 1986 Military and Paramilitary Activities Case, the ICJ addressed the responsibility for a covert naval mining operation in Nicaraguan waters (although, as the Court noted, details as to whether the mines were in internal waters or territorial sea were not provided). This operation resulted, Nicaragua claimed, in the destruction of or damage to 12 vessels, injury to 14 people, and two deaths (para 76). No substantial evidence as to mine type, or linkage to US inventory (apart from a contested report about bespoke mines being produced by the CIA) was provided.

The Nicaragua case thus indicates that responsibility for mine-laying, and the damage caused by the mines, could in some circumstances be sufficiently inferred from statement and policy evidence, even in the absence of physical evidence. A Nicaraguan FDN Fuerza Democrática Nicaragüense (Nicaraguan Democratic Force) informant testified that the United States had aided the rebels in laying mines. (para. 77). The Director of the CIA testified before the Senate that President Reagan had indeed authorized such operations, but Reagan denied it, as he was embroiled in a battle with Congress over funding Nicaraguan guerillas. (para. 78). Given these broad indications, the Court found that the United States had laid mines in Nicaraguan waters. (para. 80). Indeed, the evidence as to U.S. responsibility was almost entirely based on official statements and press reports. Nevertheless, the Court found

… that, on a date in late 1983 or early 1984, the President of the United States authorized a United States government agency to lay mines in Nicaraguan ports; that in early 1984 mines were laid in or close to the ports of El Bluff, Corinto and Puerto Sandino, either in Nicaraguan internal waters or in its territorial sea or both, by persons in the pay and acting on the instructions of that agency, under the supervision and with the logistic support of United States agents; that neither before the laying of the mines, nor subsequently, did the United States Government issue any public and official warning to international shipping of the existence and location of the mines; and that personal and material injury was caused by the explosion of the mines, which also created risks causing a rise in marine insurance rates (para 80).

Thus, the Nicaragua decision supports the American approach in the present case to hold Iran responsible for the recent mine strikes after its numerous threats to close the strait, and its repeated harassment of foreign naval and merchant shipping in the strait. The American, British and Japanese judges declined to join the Court in holding that the United States had breached its obligations to refrain from the use of force in laying the mines. (para. 292(7)). Even Judges Schwebel and Jennings, however, joined the majority in holding that by failing to “make known the existence and location of the mines laid by it,” the United States breached its obligation under customary international law. (para. 292(8)). Only Judge Oda from Japan did not agree with that conclusion. 

The 2003 Oil Platforms Case involved, inter alia, the issue of a mine strike on a US warship, the USS Samuel B. Roberts, in the Central Arabian Gulf. Mine clearance operations provided evidence – outlined in the US submissions to the Court – of the Iranian origins of the mines in the CAG. This evidence was compelling in terms of the fact that Iran previously was caught red-handed laying mines in the area, and the mine that struck the Roberts was consistent with sequence numbers and the unique anchor types used by Iran (US counter-memorial and counter-claim, 23 June 1997, e.g. Chs.  II.3, V.2.A, VI). A somewhat incredulous ICJ, however, concluded that the evidence provided – the capacity of Iran to lay these mines, the type, make, and numbering of mines being Iranian – was insufficient to attribute the specific mine strike against USS Samuel B. Roberts to Iran.

The main evidence that the mine struck by the USS Samuel B. Roberts was laid by Iran was the discovery of moored mines in the same area, bearing serial numbers matching other Iranian mines, in particular those found aboard the vessel Iran Ajr… This evidence is highly suggestive, but not conclusive. (para 71)

This test abandoned the rather lower standard of proof invoked in the Corfu Channel and the Nicaragua Cases, and the ICJ determined that U.S. retaliatory strikes against Iranian oil platforms were not justified. (para 72)


With this background in place, we can now explore some points of distinction and how they affect both attribution of responsibility, and available responses. In doing so, however, we must note two important caveats that attend this form of assessment activity. The first is that regardless of what the three ICJ cases dealing directly with mines have concluded, as a general approach, the ICJ will balance the work required of the evidence before it – particularly as to standard and methods of proof – in relation to the seriousness of the allegations it is assessing (Bosnia Genocide Case, paras 209, 211-213). Second, we must always bear in mind that attribution as a judicial determination, and attribution as a matter of international politics, are often differently assessed and differently focused.

Attaching limpet mines to the hulls of specific vessels is more targeted conduct than laying free floating or moored mines. This tends to suggest a greater degree of conscious planning and selection of targets than the indiscriminate employment of free floating or moored mines. It also requires significant capabilities, including highly trained divers and well developed covert insertion techniques, or clandestine teams placing mines on the hull. The planning and capabilities involved thus speak to both specific intention and targeted effects to a degree that the deployment of other less discriminate mine types does not. The ‘contextual appreciation’ approach of the Nicaragua Case – giving weight to policy, past practice, and political statement evidence on the part of Iran – suggests in this case that there is enough evidence to support a conclusion of Iranian responsibility.

By contrast, the Corfu Chanel case is evidentially different to the recent SOH incidents. The ‘must have known and are therefore responsible’ approach – if the evidence does indeed indicate IRGCN involvement – would create little difficulty in attributing responsibility to Iran. But the key is the sufficiency of evidence as to Iranian post-incident conduct as an indicator of the required level of knowledge, and thus responsibility to (as a minimum) warn. The Corfu Channel reasoning suggests Iranian denials (as with the Albanian denials) are fatally undermined by the associated contextual evidence – including capability, possession and type evidence – and by the post-incident conduct of the Iranian craft and personnel.

The Oil Platforms test is more circumspect, as the ICJ found the evidence in that case to be inconclusive. Evidence of Iranian capability, possession, and type of mines was unconvincing to the majority in terms of attributing the specific mine strike on the Roberts to Iran. It is likely that in the current situation, combining Iranian capability, possession, and type evidence with the footage of IRGCN activity post-incident would probably still be insufficient for the Court. With limpet mines, however, if Iranian type, batch, and attachment capability evidence is uncovered, then the specifically targeted nature of their employment will immediately overcome the direct mine-to-target causality that the ICJ implied was necessary in Oil Platforms.


In Oil Platforms, the ICJ considered that a series of attacks (not all by mines) on merchant vessels, even of the same flag, did not necessarily enliven Article 51 and the right to use force in response, because it never accepted that Iran was responsible. The Court did concede that a single attack on a warship might be sufficient to cross the armed attack threshold, however. Corfu Channel did not address the issue of attacks on merchant vessels, as the damaged vessels were warships and the killed sailors were all Naval personnel, but it unhelpfully ruled that British efforts to clear the mines violated Albanian sovereignty (p36). In Nicaragua, the damaged vessels were all merchant and fishing vessels, but the series of mine attacks was combined with other acts and conduct in reaching conclusions on use of force, so we do not gain any sense of an independent ‘quantum’ of attacks on merchant vessels as an armed attack threshold. Consequently, in the present case, unless the mine strikes can be squarely attributed to Iran, or a warship is targeted, existing case law would be highly skeptical of a use of force under Article 51 of the Charter of the United Nations. It bears mentioning, however, that the United States has criticized the Court’s failure to attribute the mine strike on USS Samuel B. Roberts to Iran.

Furthermore, whilst the ICJ in Corfu Channel explicitly denied the UK claim of self-help to clear the mines, the modern Articles on State Responsibility may validate such actions as a non-forcible but otherwise unlawful counter-measure (mine clearance) in response to the unlawful act of hampering transit passage under the regime established by Part III of the 1982 United Nations Convention on the Law of the Sea. The distinction between clearing sea mines in the water and observing and removing limpet mines emplaced on hulls, however, differentiates the cases. Ship hull search operations are certainly justified, but require flag state consent and would likely need to happen close to shore or in port.


The Corfu Channel Case, which recognized a right of navigation but denied the British any means to secure it, has been bypassed by adoption of the regime of transit passage in UNCLOS and greater resort to self-help since 1949. The right to employ other measures such as escort of merchant ships, including in those parts of the strait overlapped by Iranian territorial seas, is, however, already in play, as these are lawful protective measures against immediate threats. Escort is thus not a countermeasure because it is not an unlawful act in the first place. Furthermore, given the current manifest (albeit, on some assessments, as yet non-attributable) risks to safety of navigation at the entrance and through the Strait of Hormuz, it is not necessary to prove Iranian responsibility for anything, because escort is a fundamentally lawful incident of normal mode in the circumstances.

The United States has attributed the attacks to Iran, and this conclusion would be supported by the Nicaragua Case, which afforded greater meaning to the context and circumstantial evidence. The Oil Platforms Case, however, required more exacting levels of proof for attribution, and would suggest that the evidence in the present case does not conclusively connect Iran to the limpet mines. However, the United States’ concept of self-defense is less circumscribed than that propounded by the ICJ, and Washington has rejected both the Nicaragua and Oil Platforms decisions. U.S. rules of engagement, furthermore, permit the use of force in the face of hostile act or even simple demonstration of hostile intent. These standards have likely already been met as a matter of ROE, and thus restraint by the U.S. in the current situation is not driven by its understanding of the law of self-defence, but rather by policy choice.  


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Mohammad Rubaiyat Rahman says

June 24, 2019

It appears that legal discussions of all the three cases of the International Court of Justice (ICJ) are suitable to all kinds of situations: Peacetime; non-international armed conflict and international armed conflict.

The write up, at the beginning, has discarded the existence of international armed conflict situation in the Strait of Hormuz. The lucid explanation of the article would be more understandable if it would clarify whether the ongoing tension in the Gulf of Oman is skewed to peacetime or non-international armed conflict situation. It is necessary to grasp the relevancy of legal considerations of those three ICJ cases to the abseiling situation in the Strait of Hormuz.

There has been circulation of video displaying that Iranian naval vessel had been engaged in removing unexploded mine from the Japanese Tanker. Well, the attack on two tankers were occurred beyond the territorial water of Iran. Nevertheless, Iranian naval vessel (IRGCN) crossed their territorial sea and involved in removing mines, which might actually altered or defaced an evidence relating to intact mine/projectile.

How does the Law of the Sea (UNCLOS III) appraise such naval action by Iran in an int'l transit passage like the Strait of Hormuz?

If the mine removal action of the IRGCN is aimed to wipe evidence from the ship hull, does that act of removing mine/projectile by Iran prejudice to int’l freedom of navigation and security of sea lines of communication?

My last question is regarding naval mine countermeasure initiatives and the Law of Sea. It seems that there is absence of explicit provisions regarding mine-laying activities in the 1982 UNCLOS provision. Is there any existence of international law norm that provides some legal insights regarding actions of states to undertake naval mine countermeasure operations during peacetime?

Jasmin Johurun Nessa (University of Liverpool) says

June 25, 2019

Interesting post - great that we are talking about evidence!

However, I am not sure I would agree with the analysis that the ICJ, in the Oil Platforms case, 'abandoned the rather lower standard of proof invoked in the Corfu Channel and the Nicaragua Cases'. Instead, it could be argued that the Court in the Oil Platforms case (and Nicaragua case) adopted a different test for attribution than in the Corfu Channel case.

In the Oil Platforms and Nicaragua cases, the Court adopted a direct attribution test whereby the Court held that the State itself laid the mines. However, in the Corfu Channel case, the Court appears to have adopted an indirect attribution test whereby the Court could not accept that the State itself had laid the mines but held that it would still be responsible because the mines could not have been laid without the State's knowledge.

If we have a look at the Corfu Channel case in relation to attributing responsibility of the mines to Albania under an attribution test that determines that Albania itself had laid the mines, the references to standards of proof are always high. E.g.
*allegations did not constitute 'decisive legal proof' (p16)
*'...allegations falling short of conclusive evidence' (p16-17)
*'... a degree of certainty that has not been reached here' (p17) - Judge Winiarski, in his dissenting opinion, argued that this degree of certainty requirement should also have been applied by the Court when it addressed the UK’s argument that the mines could not have been laid without Albania’s knowledge because 'such an exceptionally grave charge against a State, as the Court has rightly said, would require a degree of certainty that has not been reached here.’ (p49)
*The Court accepted that ‘means of indirect evidence’ could be admitted in these circumstances but the Court maintained that such inferences of fact may only be drawn ‘provided that they leave no room for reasonable doubt’ (emphasis by Court)(p18)

Marco Longobardo says

June 26, 2019

Dear James and dear Prof. McLaughlin,

Many thanks for your very interesting post. I have two doubts:

1) I wonder why you consider the issue from the perspective of attribution. For me, the issue is evidentiary in nature rather than a problem regarding attribution. Or do you think that the rules on attribution embodied in Arts. 4-11 of the ILC's ARSIWA do not apply to mine strikes? (maybe because there are some special customary rules on attribution for mine strikes, as permitted by Art. 55 ARSIWA?)

2) Similarly, in relation to the Corfu Channel case, I am unsure whether the Court did attribute the mine strike to Albania. In fact, p. 22 of the judgment discusses some due diligence obligations of prevention and vigilance, rather than the mine strike itself as attributed to Albania. It seems that the Court found a violation of these due diligence primary rules rather than a breach of the rules regarding mines in naval warfare. Indeed, according to the Court:

"The obligations incumbent upon the Albanian authorities consisted in notifying, for the benefit of shipping in general, the existence of a minefield in Albanian territorial waters and in warning the approaching British warships of the imminent danger to which the minefield exposed them. Such obligations are based, not on the Hague Convention of 1907, No. VIII, which is applicable in time of war, but on certain general and well-recognized principles, namely: elementary considerations of humanity, even more exacting in peace than in war; the principle of the freedom of maritime communication; and every State's obligation not to allow knowingly its territory to be used for acts contrary to the rights of other States."

Consequently, I think that the issue here is not whether or not Albania was responsible for the mine strike, but rather, whether or not Albania had acted diligently to prevent certain uses of its territory.

What do you think about this?

All the best,