The very first problem in discussing the legality of the coalition naval enforcement measures off the coast of Yemen is that the necessary operational details of the coalition operations are, in fact, scarce in the public domain. As the footnotes of the history provided above show, the reconstruction is derived mainly from public sources, which may not be correct or complete. To further the discussion, however, I will proceed based on this history, keeping in mind that the facts may be (partly) incorrect. As mentioned in the introduction, the analysis is subdivided into four questions. Namely, does the law of blockade apply in this conflict? Has the coalition established a blockade in the legal sense of the word, a blockade stricto sensu? Are there other possible legal bases that can be applicable to these enforcement measures? And lastly, how do humanitarian considerations impact on the legality of the naval enforcement measures?
The Applicability of the Laws of Naval Warfare
The first question relates to the legal status of the conflict and the subsequent issue of the applicability of the legal regime of laws of naval warfare. The status of the ongoing conflict in Yemen is generally characterized as a NIAC between the Yemeni Government on the one hand and the Houthis on the other.Footnote 16 Sustained hostilities taking place between the Yemeni Armed Forces and a non-governmental armed group and the use of force between both has reached a high enough intensity to be classed as more than merely internal disturbances.Footnote 17 Furthermore, the Houthis appear to be organized in such a way that they are able to plan and sustain military operations and control territory.Footnote 18 With regard to the Saudi-led coalition acting in support of the Yemeni Government, one could debate whether the conflict is a separate NIAC between the coalition and the Houthis, or whether the coalition is in fact part of the NIAC between the Yemeni Government and the Houthis. Either way, it will result in a NIAC.
The legal status of a NIAC complicates the applicability of the law of blockade, as it is generally recognized that the laws of naval warfare do not apply during NIACs.Footnote 19 Although one could argue about the exact scope of the law of naval warfare and whether parts of it might actually apply during NIACs, such as the more protective ‘Geneva’ rules on sea warfare with regard to, for instance, the shipwrecked and hospital ships, it is clear that the law of blockade does not. As Heintschel von Heinegg notes: ‘It is a correct statement of the contemporary law that, absent recognition of belligerency, the parties to a non-international armed conflict are not entitled to establish and enforce a naval blockade against foreign flagged vessels’.Footnote 20 As he points out, historical application of the law of blockade during a NIAC, for instance during the American Civil War, must be viewed within the context of a recognition of belligerency. To the author’s knowledge no such statement of recognition has been made by any State in the Yemeni conflict. If the threshold of NIAC is passed in this conflict, the conclusion that must be drawn from it is that, although the laws of armed conflict applicable in a NIAC apply, the laws of naval warfare do not apply in the Yemeni conflict.
The importance of this conclusion is that, first, the parties to the conflict cannot base their enforcement authority on this subregime of the laws of armed conflict. In other words, they have no legal authority derived from the laws of naval warfare to establish and enforce a belligerent blockade. Second, and consequently, the blockading party can also not be held liable for breaching the laws of blockade, as this legal regime does not apply to the situation. The exclusion of the applicability of a certain part of international law means that, in principle, it cannot be breached. This, for instance, also implies that it does not make sense to discuss the San Remo Manual sections on humanitarian obligations in the context of the Yemeni blockade. It is, however, possible that the authority from the law of blockade has de facto been used, which would mean that it is used unlawfully. Which brings me to the second question.
Are the Established Naval Enforcement Measures a Blockade Stricto Sensu?
The second question is whether the coalition has established a blockade stricto sensu and is enforcing it as such, or whether the measures are a de facto blockade causing similar effects.Footnote 21 The importance of this question is that if a blockade stricto sensu has been established, it has been done unlawfully and, therefore, has also been unlawfully enforced. If it is not a blockade stricto sensu, firstly, there cannot be an argument of unlawfully establishing and enforcing a blockade and secondly, the (third) question arises whether there are other legal bases that may provide a possible legal ground for the measures that have been taken.
The traditional law of blockade is a historically grown balance between belligerent and neutral interests based on the situation of an international armed conflict. This body of law, apart from the one rule in the Declaration of Paris (1856),Footnote 22 is entirely based on international customary law. The most complete attempt to codify the law of blockade has been the Declaration of London (1909). The London Declaration has, however, never been ratified, and was during the First World War even abrogated by the English and French allies.Footnote 23 Today, many authorsFootnote 24 take the position that the provisions of the London Declaration and also the San Remo Manual on International Law Applicable to Armed Conflicts at Sea (1995) can serve as the substantial basis for the law of blockade. Some even consider the San Remo Manual provisions to be a codification of customary law. This is also a view recently taken by the many committees of inquiry that investigated the Israeli blockade operations.Footnote 25
The commentary in the San Remo Manual mentions that a ‘blockade is the blocking of the approach to the enemy coast, or a part of it, for the purpose of preventing ingress and egress of vessels or aircraft of all States’.Footnote 26 The sections in the San Remo Manual also embody the well-known and generally accepted conditions of notification, impartiality and effectiveness that form the basis for a blockade to be legally established and which opens the door to far-reaching authority for the blockading force. The practical result of these conditions is that, to put it simply, during a blockade nothing is meant to pass in or out of the blockaded port or coast. This is inherent to the conditions of the establishment of a blockade. As Heintschel von Heinegg mentions in the context of the Israeli Gaza blockade, ‘when one wants to maintain a blockade one has no choice but to prevent all vessels from entering or leaving the blockaded area’.Footnote 27 Two exceptions can be mentioned. The first is the authority of a blockading State to authorize the passing of humanitarian aid shipping, an action that does not affect the conditions of effectiveness or impartiality of the blockade. Second is the passing of neutral warships, which does not affect the legality of the blockade.Footnote 28
To answer the second question, the actual facts at sea are important and at the same time hard to establish. In terms of chronology, it appears that the coalition force publicly announced that they were stopping arms flowing into Yemen from the sea before the Yemeni Government formally announced it would close off the Yemeni territorial waters. There is no information available on whether the coalition actually stopped and searched vessels in the intervening time. Sands, Clapham and Ní Ghrálaigh mention that:
The intensity of the blockade has reportedly varied over time. Whereas it originally consisted of a full blockade of Yemeni ports, prohibiting all but a limited number of aid shipments, restrictions have since been somewhat reduced: vessels must now reportedly be approved and inspected by Coalition forces in order to enter Yemen’s territorial waters.Footnote 29
They may possibly be right, but be that as it may, it is clear that the situation developed into an inspection procedure in which vessels are potentially able to pass after being duly inspected, rather than a procedure of stopping all ingress and egress for the purpose of closing off the ports.Footnote 30 Apparently, the coalition naval forces did not aim to impose an actual naval blockade operation, in which the purpose is to stop the ingress and egress of all vessels. Instead, the measures are more likely aimed at conducting inspection procedures within the territorial waters of Yemen in order to stop material that might be useful against the coalition when in the hands of the enemy, such as weapons, but also other possible ‘contraband’ items, such as oil, gas and fuel. The concept of operations may indeed have resulted in a de facto blockade, with vessels having to queue, wait and possibly be refused entry into port. One notice from the UK Hydrographic Office, in a procedure to follow for vessels calling at Yemeni ports, stated that vessels must obtain permission to enter. It does however not state that no vessel can enter or leave.Footnote 31
In May 2016, the Yemeni Government announced that entry permission into Yemeni ports (Hodaida, Saleef and Makha) is to be obtained through the United Nations Verification and Inspection Mission for Yemen (UNVIM)Footnote 32 that has been installed in support of resolution 2216.Footnote 33 The UN Secretary-General stated that UNVIM is to:
facilitate the unimpeded flow of commercial goods and services to Yemen, while ensuring compliance with the arms embargo established pursuant to Security Council resolution 2216 (2015). It should provide fast and impartial clearance services for shipping companies transporting commercial imports and bilateral assistance to Yemeni ports outside of the authority of the Government of Yemen.Footnote 34
The procedure put into place by UNVIM certainly does not look as if it aims to deny all traffic entry or exit from the Yemeni ports.
Another indicator that may point in the direction that the coalition itself did not consider itself to be using the law of blockade, is that the measures are not taken outside the Yemeni territorial waters. The operational stand-off distance of a blockading force is not hampered by the international law of the sea because of the view that during international armed conflict the high seas are allowed to be used for military operations.Footnote 35 This authority is not so much connected to establishing blockades as a particular authority in blockade warfare,Footnote 36 but to the idea that in interstate warfare the global commons of the sea can be used for hostilities. The only consideration of the international law of the sea that could have some effect on the establishment is the due-regard rule that applies in international waters. Although operationally the distance taken by the blockading force is determined by military requirements, which could have taken it further out to international waters,Footnote 37 the enforcement measures with regard to Yemen remained within the limits of the territorial sea. Now that it has been established above that the laws of naval warfare do not apply, there is also no legal ground to apply the measures outside the territorial waters.
Interestingly, the public press statements from the coalition were getting wise to the terminology with regard to the naval enforcement measures. Where at the beginning of the operation the spokesmen spoke of a blockade, this was changed into a denial of having established a blockade stricto sensu. In 2016 the military spokesperson stated:
The Saudi-led coalition denied on Tuesday it had imposed a ‘blockade’ on Yemen, saying instead that it was only controlling access to the country to prevent pro-Iran rebels from obtaining arms. ‘No, there is no blockade’, coalition spokesman Major General Ahmed Assiri told AFP. ‘There is control based on international law… Control is different from blockade, which means that nobody can enter or leave the country’, he said. Assiri also spoke of ‘restriction’ and ‘controlled freedom of movement’.Footnote 38
Based on what is publicly available, there are sufficient grounds to conclude that no blockade stricto sensu has been established, but measures that may have a similar effect. If this is indeed the case, it is hard to argue that a breach of international law has taken place by unlawfully using the legal authority of the law of blockade.Footnote 39
Other Legal Bases to Establish Naval Enforcement Measures
Let us assume that the laws of naval warfare do not apply and no blockade stricto sensu has been established. Still, naval enforcement measures are in place. Is there any other legal basis that may serve to support these measures? Two legal bases can be looked at in particular. First is the combination of State consent and the international law of the sea. Second is the Security Council’s resolution 2216.
The earlier mentioned statement of 10 April 2015 stated that the enforcement measures were to be undertaken within the territorial sea of Yemen. The Yemeni Government itself mentioned that it is using force in self-defence, in the context of Article 51 of the UN Charter. The request to join Yemen against the Houthis was made in the same context. Were one to follow this path, arguably, the coalition would be acting on the basis of collective self-defence against the Houthi opponents, as the coalition is acting on the request and with the consent of the Yemeni Government. The Yemeni Government has sovereign powers over its territorial and internal waters. Within the 12 nm space of the territorial waters Yemen has, therefore, sovereign powers with respect to controlling the shipping and the entering or leaving of ports. Within the limitations of Article 25(3) of the Law of the Sea Convention (UNCLOS) a State can also suspend the right of innocent passage. This Article reads:
3. The coastal State may, without discrimination in form or in fact among foreign ships, suspend temporarily in specified areas of its territorial sea the innocent passage of foreign ships if such suspension is essential for the protection of its security, including weapons exercises. Such suspension shall take effect only after having been duly published.
Whatever is taking place exactly with regard to inspection and refusals of entries into ports within the territorial waters of Yemen, it is within the power of a sovereign State and does not breach any authority given to other users of the sea based on the international law of the sea. A very strict ingress policy or even the closure of ports and the suspension of innocent passage essential for the protection of State security may be possible. Although shipping agencies have at the beginning of the conflict been advising keeping clear of the Yemeni territorial waters, it appears that the latter measure of suspending innocent passage has not been formally taken.Footnote 40 This, however, does not stop Yemen’s right to implement a very strict ingress procedure into the Yemeni ports.
The second legal basis that can be considered is UN resolution 2216 (2015). The core issue that emerges here is the geographical scope of the imposed arms embargo and what authority the resolution mandates in the different maritime zones, in particular in the territorial sea and the high seas. With regard to the territorial sea, from the resolution’s key paragraphs (14–17) it is clear that the resolution calls upon States to enforce the arms embargo within the territory of States. Yemen’s territory is no exception to this. Yemen can, therefore, enforce the resolution within its territory, which includes the internal waters and territorial sea. A possible legal basis in these maritime zones therefore exists for enforcing the arms embargo. Actual enforcement of the arms embargo should be governed by national legislation on UN sanctions implementation.
With regard to the high seas, the point to underline is that the resolution does not explicitly authorise the enforcement of a maritime embargo operation at sea. Even if one were to push the text of the resolution to implicitly read as a basis for enforcing the resolution on the high seas, it would be under the limitation that the enforcement would need to be in line with the international law of the sea, as the resolution expressly states. In contrast to the law of naval warfare, the international law of the sea does not provide for any enforcement measures on the high seas that are even remotely akin to blockade measures. Rather, the exclusive jurisdiction of the flag State is leading in that regard. The resolution can, therefore, not be a legal basis for enforcing an arms embargo on the high seas.
Interestingly, patrolling of the high seas around Yemen apparently does happen. According to the UN Panel of Experts on Yemen:
63. Coastal dhows, if en route to Houthi-Saleh-controlled ports on the west coast of Yemen, even if routed via a transit point in Djibouti or Somalia, must pass from the Gulf of Aden into the Red Sea through the busy Bab al-Mandab strait, which is 28 km wide. This is well patrolled by the Combined Maritime Forces, the United States Navy Fifth Fleet and the Royal Saudi Navy. If sent in very small consignments on coastal dhows, it is probable that some shipments would arrive, but many would inevitably be interdicted by naval patrols. The Panel has seen no evidence of any maritime seizures to date on this route, which strongly suggests that it is not being actively exploited.Footnote 41
According to the same report, during 2015 and 2016 four interdicted ships had cargo that was confirmed seized by Australian and American warships:
66. There were only four confirmed seizures of weapons in the Arabian Sea and the Gulf of Aden by the Combined Maritime Forces or the United States Navy Fifth Fleet during 2015 and 2016, together with an alleged seizure by the coalition led by Saudi Arabia in 2016 (see table 2).
These vessels and weapons were, however, seized under the arms embargo mandates of UN resolutions 2182 (2014) and 2244 (2015) that were set up with regard to the Somalia situation.Footnote 42 Although the proximity to other, overlapping, conflict areas is creating other possible legal bases for seizing arms in the maritime area on the high seas around the Horn of Africa, it does not create a ground for seizing weapons on the high seas with regard to Yemen. Following this wider look at different conflicts taking place in the Yemeni region, even if one were to argue that yet another conflict must be taken into consideration, namely the conflict between Yemen and the United States and terrorist organizations such as Al Qaida and/or IS, still no conclusion can be drawn that an international armed conflict exists to which the laws of naval warfare would apply. To conclude, the resolution with regard to Yemen imposes an arms embargo that States can enforce within their own territory. There is, however, no authority that can be derived from the resolution to enforce an arms embargo outside the territorial waters of a State.
There is no clear statement by the Yemeni Government on what the exact legal basis of the naval measures is. The coalition spokesperson, Major General Ahmad Assiri, stated in this regard that:
‘If a boat leaves from Djibouti, before reaching Hodeida (port in western Yemen), our forces board the vessel to ensure the cargo is legal and complies with Resolution 2216, adopted by the UN Security Council in April 2015 and prohibiting the delivery of arms to the rebels in Yemen’, he said.Footnote 43
It can be argued that the combination of consent and conducting coalition operations only in the territorial sea of Yemen does not breach international law and can arguably be said to be in support of the UN resolution. Were these naval measures to be taken outside the territorial sea, then the resolution would not support such operations, nor would this be possible under the general international law of the sea. The set-up of the UNVIM procedures, based upon the UN resolution, for entering Yemeni ports and the statement of the coalition spokesperson gives a good indication for the resolution being part of the legal basis for the inspections, or at least legitimizes the coalition’s activities. One other reference that supports that is the view of Akande and Gillard, which mentions that ‘The Saudi-led coalition was overseeing the implementation of the arms embargo imposed by the Security Council…’.Footnote 44
Humanitarian Considerations and Blockade
The fourth and last question to remark on relates to the issue of humanitarian considerations in relation to blockades. As mentioned earlier, there is a widely-held view that the naval measures have an immensely negative impact on the civilian population. Support for the unlawfulness of the naval measures is looked for and found within the law of blockade and the San Remo Manual, the latter of which contains a section on the lawfulness of blockades in relation to starvation. If, however, the approach set out above is followed whereby the view is put forward that the law of blockade does not apply, it does not make real sense to discuss the relationship between humanitarian considerations and the law of blockade. The consequence of the conclusions to the first three questions dismissed the application of the law of blockade and its possible humanitarian requirements. It would probably be better to argue that a State has breached its obligations under the rules of the prohibition on starvation or access to humanitarian aid than to confuse this with the law of blockade, which does not apply. The naval measures may not be a violation of the laws of naval warfare, but it may arguably be unlawful under the broader rules of the laws of armed conflict, such as Articles 14 and 18 of Additional Protocol II to the 1949 Geneva Conventions (APII) concerning the population’s access to humanitarian relief. The debate would then centre on the question of whether the naval measures are conducted in such a manner that they cause starvation, whether consent for relief shipping is withheld unlawfully, and whether enough is done to allow humanitarian relief to pass through the inspections.Footnote 45 Whether they actually do, falls outside the scope of this article. What is at least made clear here is that possible unlawfulness cannot be determined by looking at the law of blockade.
Although in this particular situation it is argued that the law of blockade does not apply, but if it did, a few points on the relationship between humanitarian considerations and the law of blockade can be raised. Currently the only humanitarian consideration the law of blockade contains is that a blockading force can, under the conditions of the blockading force, allow aid shipping to pass without hampering the condition of effectively and impartially establishing a blockade. An effective blockade will most certainly, and in fact needs to, have an impact; that is the operational purpose of a blockade.Footnote 46 The impact of a blockade can depend on the purpose of the blockade, which can be military or economic, or both.Footnote 47 Interestingly, in section 102 of the San Remo Manual the humanitarian consideration of starvation and the conditions for establishing a lawful blockade have been merged into one rule. It states:
102. The declaration or establishment of a blockade is prohibited if:
(a) it has the sole purpose of starving the civilian population or denying it other objects essential for its survival; or
(b) the damage to the civilian population is, or may be expected to be, excessive in relation to the concrete and direct military advantage anticipated from the blockade.
Not surprisingly, this section is often quoted in the context of the unlawfulness of the Yemeni enforcement measures. In an earlier article I suggested with regard to this section of the San Remo Manual that the law of blockade has seen an increasing willingness to embrace more humanitarian conditions or principles that put further restraints on the manner in which a blockade is established and enforced.Footnote 48 The Yemeni situation is another case in point where the humanitarian considerations and blockade have been merged together in a legal discussion. But viewed realistically, no State will probably ever state that their blockade has the intentional aim of starving a population. Discussion will rather centre on the second paragraph of section 102, in the context of whether enough food and other essential products are entering into Yemen so that the blockade can be deemed proportional. What this also implies, is that if the damage to the civilian population is not excessive as regards the blockade in relation to the direct military advantage anticipated from the blockade, it is not prohibited. In other words, the effect (rather than the purpose) of starvation does not by definition render a blockade unlawful.Footnote 49
Finally, sections 103 and 104 of the San Remo Manual are also interesting to note, because they deal with humanitarian aid shipping.
103. If the civilian population of the blockaded territory is inadequately provided with food and other objects essential for its survival, the blockading party must provide for free passage of such foodstuffs and other essential supplies, subject to:
(a) the right to prescribe the technical arrangements, including search, under which such passage is permitted; and
(b) the condition that the distribution of such supplies shall be made under the local supervision of a Protecting Power or a humanitarian organization which offers guarantees of impartiality, such as the International Committee of the Red Cross.
104. The blockading belligerent shall allow the passage of medical supplies for the civilian population or for the wounded and sick members of armed forces, subject to the right to prescribe technical arrangements, including search, under which such passage is permitted.
The above-mentioned sections of the San Remo Manual attempt to translate the API and APII obligations on access to humanitarian relief to a maritime environment. They are progressive in the sense that they underline that, for instance, the blockading Party must provide free passage to humanitarian aid, whereas the traditional law of blockade only went as far as to accept that letting humanitarian aid pass should not hamper the effectiveness of the blockade. They are also progressive in the sense that proportionality is introduced into the question of unlawfulness. The merging of the rule regarding starvation and the law of blockade is tempered as it appears to need an intent, whereas on land the dimension of unlawfulness is based on the fact that military actions cause starvation.