Germany Supports Expansive Interpretation of the Right to Self-Defence Against Attacks by the Houthis on Commercial Shipping in the Red Sea

Published: 23 January 2024  Author: Stefan Talmon

On 19 November 2023, the Iranian-Backed Houthi movement, which controlled large parts of Yemen, began attacking commercial vessels transiting the Red Sea in order to show their support for the terrorist organisation Hamas in its fight against Israel. The Houthis declared they were targeting ships which were Israeli-owned, flagged or operated, or which were heading to Israeli ports. However, the attacks had a broader impact on international commercial shipping. Nearly 15 percent of global seaborne trade passes through the Red Sea, including 8 percent of global grain trade, 12 percent of seaborne-traded oil and 8 percent of the world’s liquefied natural gas trade. As a result of the attacks, international shipping companies decided to reroute their vessels around the Cape of Good Hope rather than sail them through the Red Sea and the Suez Canal. This led to major disruptions of international shipping and, consequently, international supply lines. On 3 January 2024, the Federal Government joined thirteen other governments in a statement on the Houthi attacks, which read in part:

Ongoing Houthi attacks in the Red Sea are illegal, unacceptable, and profoundly destabilizing. There is no lawful justification for intentionally targeting civilian shipping and naval vessels. Attacks on vessels, including commercial vessels, using unmanned aerial vehicles, small boats, and missiles, including the first use of anti-ship ballistic missiles against such vessels, are a direct threat to the freedom of navigation that serves as the bedrock of global trade in one of the world’s most critical waterways. … We remain committed to the international rules-based order and are determined to hold malign actors accountable for unlawful seizures and attacks.

On 9 January 2024, the Houthis launched their largest attack yet on international shipping. US and UK forces shot down eighteen drones and three missiles over the Red Sea launched by the Houthis. US Central Command issued a statement, saying that

[The] Houthis launched a complex attack … into the Southern Red Sea, towards international shipping lanes where dozens of merchant vessels were transiting. … This is the 26th Houthi attack on commercial shipping lanes in the Red Sea since Nov. 19. There were no injuries or damage reported.

The UK Defence Secretary said that the British destroyer HMS Diamond intervened after the drones were ‘heading for her and commercial shipping in the area’. He also added: ‘We will take the action needed to protect innocent lives and the global economy’.

On 10 January 2024, the United States and Japan introduced a draft resolution in the UN Security Council, which condemned in the strongest terms the at least two dozen Houthi attacks on merchant and commercial vessels and demanded that the Houthis immediately cease all such attacks. The draft resolution also affirmed in operative paragraph 3:

the exercise of navigational rights and freedoms by merchant and commercial vessels, in accordance with international law, must be respected, and takes note of the right of Member States, in accordance with international law, to defend their vessels from attacks, including those that undermine navigational rights and freedoms.

The latter paragraph proved controversial. The Russian representative called for the deletion of the reference to the right of States to defend one’s vessels from attacks as there was no such right in international law. He added: ‘That innovation looks seriously dubious from both a legal and a political point of view.’ The US representative, on the other hand, declared that it was ‘long established that States have a right to defend merchant and commercial vessels from attacks. That is what the United States and the United Kingdom did yesterday when our ships came under attack by the Houthis. If the Houthi attacks continue, there will be consequences.’

The draft resolution received eleven votes in favour, none against and four abstentions (Algeria, China, Mozambique, Russian Federation), and was adopted as resolution 2722 (2024). Speaking in explanation of vote after the vote, the Russian representative stated:

We note that operative paragraph 3 does not establish a right of States to defend their ships from attacks — that does not exist. All activities under that paragraph, as stated in the paragraph itself, must be carried out strictly within the framework of existing international law. …

According to the Permanent Representative of the United States, it turns out that her country equates the protection of commercial vessels with self-defence. In voting together with Britain against the proposed amendment … to operative paragraph 3, the United States has in fact revealed its hand clearly. It showed that their aim behind advancing the resolution was precisely to give themselves a free hand at loosely interpreting the right to defend their ships for the purpose of self-defence. We would caution our American colleagues to refrain from that type of conduct in this context.

The representative of Slovenia also underlined that ‘our interpretation of operative paragraph 3 provides that any response to attacks in the Red Sea must be … within the strict conditions of the exercise of self-defence.’

Only one day later, on 11 January 2024, the United States and the United Kingdom launched over fifty air and missile strikes against Houthi forces and positions across Yemen. They targeted missile, radar and unmanned aerial vehicle capabilities used to carry out attacks against vessels operating in the Red Sea. The United States said that sixty targets across twenty-eight sites were hit. Following the airstrikes, US President Joe Biden issued a statement, which read in part:

These strikes are in direct response to unprecedented Houthi attacks against international maritime vessels in the Red Sea—including the use of anti-ship ballistic missiles for the first time in history. These attacks have endangered U.S. personnel, civilian mariners, and our partners, jeopardized trade, and threatened freedom of navigation. More than 50 nations have been affected in 27 attacks on international commercial shipping. Crews from more than 20 countries have been threatened or taken hostage in acts of piracy.  More than 2,000 ships have been forced to divert thousands of miles to avoid the Red Sea—which can cause weeks of delays in product shipping times. And on January 9, Houthis launched their largest attack to date—directly targeting American ships. …

These targeted strikes are a clear message that the United States and our partners will not tolerate attacks on our personnel or allow hostile actors to imperil freedom of navigation in one of the world’s most critical commercial routes.

The US Secretary of Defence also issued a statement, which explained:

Today, a coalition of countries committed to upholding the rules-based international order demonstrated our shared commitment to defending U.S. and international vessels and commercial vessels exercising navigational rights and freedoms from illegal and unjustifiable attacks.

In a letter to the UN Security Council, in accordance with Article 51 of the UN Charter, the United States explained their action as follows:

[T]he United States … has undertaken discrete strikes against Houthi facilities in Yemen in response to a series of armed attacks by Houthi militants over the last few months, including several attacks against United States Navy ships in the Red Sea. The Houthis’ outrageous attacks on vessels in the Red Sea, the Bab al-Mandeb strait and the Gulf of Aden using one-way unmanned aerial vehicles, anti-ship cruise and ballistic missiles, a helicopter-borne commando assault and small boats threaten the region’s stability and have serious economic impacts for the global community. The Houthis have conducted more than two dozen attacks on commercial vessels since mid-November, including the 19 November Houthi seizure of the M/V Galaxy Leader. On several occasions, Houthi-launched systems have been directed towards United States Navy ships, necessitating the activation of defensive systems to safeguard the ships and their crews. Houthi militants also shot at United States Navy helicopters on 31 December while the Navy helicopters were aiding a commercial vessel that Houthis were attempting to board. On 9 January 2024, the Houthis perpetrated their largest attack in the Red Sea, with multiple unmanned aerial systems, anti-ship cruise missiles and ballistic missiles targeting United States Navy vessels. There is a continuing threat of additional attacks against other vessels in the region and to the safety of United States Navy ships and personnel patrolling the Red Sea. …

In response to these attacks and the continuing threat of future attacks, on 11 January, the United States … conducted discrete strikes against Houthi facilities in Yemen that facilitate Houthi attacks in the Red Sea region, including air and coastal surveillance radar sites, as well as unmanned aerial system and missile facilities and launch sites. These necessary and proportionate strikes were taken after non-military options proved inadequate to address the threat. The strikes were conducted to degrade and disrupt the ongoing pattern of attacks threatening the United States and deter the Houthi militants from conducting further attacks threatening merchant and commercial vessels transiting the Red Sea. These military responses will preserve navigational rights and freedoms, both for naval ships and for commercial vessels, in this important maritime passageway. …

The United States took this necessary and proportionate action consistent with international law and in the exercise of the United States’ inherent right of self-defence as reflected in Article 51 of the Charter of the United Nations. The United States will take further action against the Houthis as may be necessary in the exercise of its inherent right of self-defence to respond to future attacks or threats of attacks against the United States.

While the United States invoked the right to self-defence, it did not provide any additional justification for the exercise of that right against the Houthis, a non-State movement within the territory of another State – Yemen – that was not responsible for the stated armed attack against the United States. There is no mention of consent by the Government of Yemen regarding the attack on the Houthis or to the controversial ‘unwilling and unable’ doctrine. However, any cross-border exercise of the right to self-defence must be necessary in order to be lawful. It is for that reason that the United States has claimed, for example, in cases of self-defence against terrorist or militia groups in Syria, that ‘the government of the State where the threat is located is unwilling or unable to prevent the use of its territory by non-State militia groups responsible for such attacks.’ It is unclear whether the omission of the unwilling or unable doctrine in this case was just an oversight or whether, in case of stabilized local de facto authorities in parts of a State, it is automatically to be assumed that the State’s government is unable to prevent the territory under the control of the de facto authorities from being used for armed attacks on other States.

In a statement to the House of Commons, British Prime Minister Sunak also justified the attacks with the right to self-defence, stating:

Since 19 November, Iran-backed Houthis have launched over 25 illegal and unacceptable attacks on commercial shipping in the Red sea, and on 9 January they mounted a direct attack against British and American warships. They fired on our ships and our sailors—it was the biggest attack on the Royal Navy for decades—and so we acted. We did so in self-defence, consistent with the UN charter, and to uphold freedom of navigation, as Britain has always done.

In a letter to the UN Security Council, the United Kingdom informed the Council that it had ‘conducted precision strikes against Houthi military targets on the territory of Yemen in exercise of the inherent right of individual self-defence’ in response to a series of attacks by the Houthis on vessels in the Red Sea, including the Royal Navy destroyer HMS Diamond.

On 12 January 2024, the UN Security Council discussed the air strikes in Yemen. The representative of the United States said that the strikes aimed to disrupt and degrade the Houthis’ ability to continue their attacks and that they were consistent with the inherent right to self-defence under Article 51 of the UN Charter. Since November 2023, 2,000 ships had been forced to divert thousands of miles to avoid the Red Sea — affecting fifty nations — with twenty-seven attacks on commercial shipping. This position was echoed by the representative of the United Kingdom, who stated that her country had taken ‘limited, necessary and proportionate action in self-defence alongside the United States.’ The Russian delegate, on the other hand, argued that the exercise of the right to self-defence did not apply to commercial shipping. The Swiss representative distinguished between the right of a State to defend its vessels from attack and a State’s right to self-defence against an armed attack, recalling that:

[R]esolution 2722 (2024) underscores Member States’ right to defend their vessels from attacks — including those that undermine navigational rights and freedoms.  However, this is strictly limited to military measures to intercept attacks against merchant vessels and warships to protect said vessels and the persons on board.  In this context, any military operation that goes beyond this immediate protection need would be disproportionate — and not covered by the resolution.

The airstrikes were condemned by Iran which accused the United States and the United Kingdom of a ‘serious violation of international law … in committing acts of military aggression against Yemen.’ In a letter to the UN Security Council, Iran wrote:

The United States and the United Kingdom’s invocation of the right of self-defence under Article 51 of the Charter to justify their internationally wrongful acts is misleading and lacks a legal foundation in international law. Moreover, resolution 2722 (2024) explicitly emphasizes the adherence of Member States to international law. … In this legal context, Iran vehemently rejects and condemns any arbitrary and misleading interpretation of resolution 2722 (2024) by the United States and its allies, aiming to justify their use of illegal force and military aggression against Yemen.

In contrast, Germany defended the US and British airstrikes against the Houthis as being ‘in accordance with the inherent right of individual and collective self-defence.’ On 12 January 2024, Germany joined nine other States in a statement, which read:

Recognizing the broad consensus as expressed by 44 countries around the world on December 19, 2023, as well as the statement by the UN Security Council on December 1, 2023, condemning Houthi attacks against merchant and commercial vessels transiting the Red Sea, our governments issued a joint statement on January 3, 2024, which called for the immediate end of illegal attacks and warned that malign actors would be held accountable should they continue to threaten lives, the global economy, and the free flow of commerce in the region’s critical waterways.

Despite this strong warning, attacks in the Red Sea have continued, including the launch of numerous missiles and one-way attack aerial vehicles against ships in the Red Sea on January 9, 2024, including U.S. and UK vessels. On January 10, 2024, the UN Security Council passed UNSCR 2722, which also condemned these attacks and demanded that they cease.

In response to continued illegal, dangerous, and destabilizing Houthi attacks against vessels, including commercial shipping, transiting the Red Sea, the armed forces of the United States and United Kingdom, with [non-operational] support from the Netherlands, Canada, Bahrain, and Australia, conducted joint strikes in accordance with the inherent right of individual and collective self-defence, consistent with the UN Charter, against a number of targets in Houthi-controlled areas of Yemen. These precision strikes were intended to disrupt and degrade the capabilities the Houthis use to threaten global trade and the lives of international mariners in one of the world’s most critical waterways.

The Houthis’ more than two dozen attacks on commercial vessels since mid-November constitute an international challenge. Today’s action demonstrated a shared commitment to freedom of navigation, international commerce, and defending the lives of mariners from illegal and unjustifiable attacks.

Our aim remains to de-escalate tensions and restore stability in the Red Sea, but let our message be clear: we will not hesitate to defend lives and protect the free flow of commerce in one of the world’s most critical waterways in the face of continued threats.

During the regular government press conference on 17 January 2024, the federal government was asked to explain the legal basis for the US and British attacks on the Houthi positions in Yemen. A spokesperson for the Federal Foreign Office referred to the above statement but then continued:

But I would also like to point, once again, to a decision by the UN Security Council of 10 January. There was a resolution introduced by the United States and Japan on the Houthi attacks on shipping in the Red Sea. The Security Council made it clear that all members of the United Nations have the right, in accordance with international law, to defend their ships against attacks, including attacks affecting the rights and freedoms of navigation. The text of the resolution affirms that, under international law, the exercise of rights and freedoms of navigation must be respected and also states that States have the right to defend their ships against attacks.

Confronted with the fact that to date not a single ship flying the British or US flag had been attacked, the spokesperson replied:

The Houthi attacks on ships in the Red Sea belonging to many international partners and flying the flags of many different States are taking place and are continuing. That is why I will say again in principle: These attacks are completely unacceptable and must stop.

UN Security Council Resolution 2722 (2024), which the spokesperson referred to, however, did not establish a legal basis for the use of force by the United States and United Kingdom against Houthi positions in Yemen. In particular, the resolution was not a ‘decision’ under Chapter VII and did not provide any authorisation for the use of force. On the contrary, it reaffirmed that ‘international law, as reflected in the United Nations Convention on the Law of the Sea of 10 December 1982 (UNCLOS), sets out the legal framework applicable to activities in the oceans, including countering illicit activities at sea.’ In addition, the Security Council expressly affirmed ‘its  respect for the sovereignty and territorial integrity of the coastal States of the Red Sea.’ As pointed out by the representative of Switzerland in the Security Council, the right of States to defend their vessels from attack, is not the same as a right to use force in self-defence against the attacker.

In their joint statement of 12 January 2024, Germany and the nine other States invoked ‘the inherent right of individual and collective self-defence’ in order to justify the United States’ and the United Kingdom’s use of force against the Houthis in Yemen. However, it must be noted at the outset that despite having referred to attacks on vessels of other States, neither of the two States had relied in their letters to the UN Security Council on the right of ‘collective self-defence’. On the contrary, the United Kingdom had expressly relied on ‘the individual right of self-defence.’ Any collective exercise of the right of self-defence would also have required the (other) attacked States to declare that they had been attacked and request that the United States and the United Kingdom come to their help in the exercise of the right of collective self-defence. No such declarations were made.

Germany and the other States embraced the long-standing view of self-defence of the United States which considers any use of force against a vessel flying the flag of the United States – irrespective of warship or commercial vessel – an armed attack on the United States. Such an expansive understanding of the right to self-defence in Article 51 of the UN Charter is difficult to reconcile with international law as reflected in the jurisprudence of the International Court of Justice (ICJ).

In the case of the right to individual self-defence, States exercising that right must have been the victim of an armed attack. The attacks by the Houthis against ships in the Red Sea would have had to be made upon the United States and the United Kingdom. It is disputed whether attacks on individual commercial and merchant vessels outside the territory of their home States can be equated with an attack on the State itself, and are therefore to be regarded as an ‘armed attack’ within the meaning of Article 51 of the Charter of the United Nations. However, there is general agreement that any attack on a merchant vessel can constitute an attack only on the flag State of the vessel. The nationality of the vessel’s owner, operator, crew, or cargo is not determinative of the victim of the armed attack. There was no suggestion that any US or UK flagged commercial vessel had been attacked by the Houthis. The vessels targeted sailed under the flags (of convenience) of Panama, the Bahamas, Liberia, Singapore or the Marshall Islands.

Warships are generally considered to be an external manifestation of the State. An attack against a warship, even if outside the State’s territory, may thus, in principle, give rise to the right to self-defence. While in their public statements and letters to the UN Security Council, the United States and the United Kingdom focused mainly on attacks on commercial shipping in the Red Sea, both also claimed, albeit in quite unspecific terms, that one or more of their warships in the Red Sea had been attacked by the Houthis. For example, the United States spoke of Houthi-launched systems having ‘been directed towards United States Navy ships’,  and the United Kingdom referred to drones ‘heading for [HMS Diamond] and commercial shipping in the area.’ This raises the question of whether the drones and missiles launched by the Houthis were actually ‘aimed specifically’ at the warships of the two countries as required by the ICJ, or whether they were directed at commercial vessels in the vicinity of the warships. The burden of proof of the facts showing the existence of an actual attack on their warships rests on the two States.

The attacks on the Houthi installations in Yemen were only justified as an exercise of the right of individual self-defence, if the attacks on the US and UK warships ‘were of such a nature as to be qualified as “armed attacks” within the meaning of that expression in Article 51 of the United Nations Charter.’ The ICJ distinguishes ‘the most grave forms of the use of force (those constituting an armed attack) from other less grave forms.’ Thus, not every use of force qualifies as an ‘armed attack’. In other words, the use of force by the Houthis must have crossed the threshold of an ‘armed attack’.

The use of force against individual ships, even warships, does not automatically amount to an armed attack. In the Oil Platforms case, the ICJ was concerned with a missile attack on an US flagged tanker – the Sea Isle City. The incident caused damage to the ship and injured six crew members. The United States claimed that the attack on the Sea Isle City was the seventh involving anti-ship cruise missiles in the area in 1987. The ICJ held that the specific attack on the Sea Isle City, ‘either in itself or in combination with the rest of the “series of … attacks” cited by the United States’ did not constitute an ‘armed attack’ on the United States of the kind that the Court qualified as a ‘most grave’ form of the use of force justifying self-defence.

On 14 April 1988, the warship USS Samuel B. Roberts struck a mine in international waters. Ten US sailors were injured, one seriously, and the ship was damaged. The United States claimed that the mining was an armed attack giving rise to the right of self-defence. While the ICJ did not exclude the possibility that the mining of a single military vessel might be sufficient to bring into play the inherent right of self-defence, it held that the mining of the US warship did not suffice ‘in itself to justify action in self-defence, as amounting to an “armed attack”. Against the background of these precedents and in view of the circumstance of the present case, including the rather unspecific assertions of attacks on US and UK warships and the fact that no ship had been damaged or sailor injured, the threshold of an ‘armed attack’ was not crossed.

In any case, the attacks on the Houthis were neither necessary nor proportional to the stated armed attacks on the warships of the two countries. In the Nicaragua case, the ICJ endorsed the view that ‘whether the response to the attack is lawful depends on the observance of the criteria of the necessity and the proportionality of the measures taken in self-defence.’ On 9 January 2024, United States and British forces attacked more than 60 targets at 28 different locations in Yemen, using more than 150 precision-guided munitions. The stated aim of the military operation was not just to defend US and British warships against attacks by the Houthis but to preserve navigational rights and freedoms of merchant and commercial vessels transiting the Red Sea generally.

The principle of necessity means that force may be used only if necessary for the purpose of countering, repelling or intercepting an armed attack. Once an armed attack has ceased, there is no longer any need to repel it. In case of a single use of force against a warship (as distinguished from a general situation of armed conflict), the attack is terminated when the incident is over. The stated attack on US and UK warships occurred on 9 January 2024; counter-force, however, was used only two days later. There was thus no temporal or material link between the use of force and the attack allegedly triggering it. It was probably for that reason that the United Kingdom also referred to an ‘ongoing risk to British ships’, and the United States spoke of ‘the continuing threat of future attack’. Such an unspecified ‘risk’ or ‘threat’, however, is not sufficient to justify any use of force in anticipatory self-defence. The use of force by the United States and the United Kingdom must therefore be regarded more as an act of deterrence, as a warning to the Houthis not to continue their attacks on commercial vessels in the Red Sea or as retaliation and punishment, but not as self-defence.

The attacks on the Houthi positions in Yemen also were not proportionate to the stated attacks on the warships. Counter-force must not be excessive in relation to the objective of repelling the attack. In the Oil Platforms case, the ICJ was concerned with the alleged mining by Iran of a US warship in international waters which injured ten US sailors, one seriously, and damaged the ship. In response, the United States bombed two Iranian oil platforms as part of a more extensive military operation against Iran, designated ‘Operation Praying Mantis’, in which damage was done to a number of targets, including the destruction of two Iranian frigates and other Iranian naval vessels and aircraft. Assessing the proportionality of the US response, the ICJ stated:

[T]he Court cannot assess in isolation the proportionality of that action to the attack to which it was said to be a response; it cannot close its eyes to the scale of the whole operation, which involved, inter alia, the destruction of two Iranian frigates and a number of other naval vessels and aircraft. As a response to the mining, by an unidentified agency, of a single United States warship, which was severely damaged but not sunk, and without loss of life, neither ‘Operation Praying Mantis’ as a whole, nor even that part of it that destroyed the Salman and Nasr platforms, can be regarded, in the circumstances of this case, as a proportionate use of force in self-defence.

Against the background of this finding, the use of force by the United States and the United Kingdom was also disproportionate.

The right of self-defence in Article 51 of the UN Charter is limited to the use of force that is necessary and proportional to repel an ‘armed attack’. It does not allow for the use of force by a State to protect its perceived security, economic or other interests. The protection of navigational rights and freedoms against illegal attacks, as worthy a cause that may be, does not allow for the use of force in self-defence. There is no right of self-defence against attacks on international commercial shipping. The ICJ has rightly adopted a restrictive interpretation of the right to self-defence. The more expansive interpretation of the notion of self-defence advocated for by the United States and endorsed in the present case by Germany runs the risk of easily getting out of hand, triggering larger-scale international armed conflict, and thus running counter to the purposes of the United Nations Charter.

Category: Use of force

DOI: 10.17176/20240124-004325-0