Conceptualizing IHL: Legality of the Targeting of Merchant Ships

Introduction

The Russian full-scale invasion of Ukraine in 2022 has consisted of an ongoing armed conflict on land as well as at sea.

In 2022, several merchant vessels in Ukrainian waters were attacked.  These included the vessels “Yasa Jupiter,” “Namura Queen,” “Millennial Spirit,” “Lord Nelson,” and “Helt.” These vessels were all merchant ships, flying the flags of countries neutral to the conflict. Although the origin of the attacks remains unconfirmed, contemporaneous reporting indicated that the Russian military were responsible.

In July 2023, the Russian Defense Ministry announced that it would treat all vessels sailing to Ukrainian ports as military objectives, regardless of their flag or cargo.  That same week, Russia also announced it would not renew an UN-backed deal allowing Ukraine to export grain through the Black Sea. Abandoning the deal, one of the few diplomatic “successes” since the start of the war, meant that grain can no longer be exported safely from three key Ukrainian ports (Chornomorsk, Odesa, and Yuzhny/Pivdennyi). Any vessel leaving or entering a Ukrainian port will be treated by Russia as a legitimate military target.

Historical Parallels

The targeting of civilian ships in the Russian-Ukrainian conflict is not without historical precedent.  One notorious example is Germany’s U-boat campaign against merchant shipping during World War I. Initially, Germany followed so-called “prize rules,” which meant surfacing to search ships and allow civilians to escape. However, the Germans later adopted unrestricted warfare due to Britain’s effective use of “Q-ships” which were armed merchant ships with a military crew – essentially making them warships – in order to lure U-boats to the surface so that they could be attacked.

On February 4, 1915, Germany declared a war zone around Britain, sinking merchant ships without warning. This “unrestricted submarine warfare” angered neutral countries. The tactic was abandoned on September 1, 1915, after American lives were lost on the torpedoed liners “Lusitania” and “Arabic,” both flying the neutral American flag en route from New York to Liverpool. Germany attempted to justify the attacks by claiming that the vessels were carrying military materiel and munitions.

Under intense public and political pressure, Germany stopped unrestricted naval warfare in September 1915 but nevertheless reinstated it in February 1917. Between February and April 1917, German U-boats sank over 500 merchant ships, with an average of 13 ships sunk each day in the second half of April.

During the Iran-Iraq War in the 1980s, hundreds of commercial ships also faced attacks when both countries targeted each other’s oil tankers and cargo vessels in the Persian Gulf. These attacks included missile strikes, mine-laying, and naval battles, severely disrupting maritime trade and oil transport. 

More recently, over 50 merchant ships have been attacked in the Red Sea since October 2023 by Houthi rebels operating out of Yemen. In March 2024, Houthi rebels sunk the Belize-flagged “Rubymar” as part of their operations to disrupt crucial shipping lanes in response to the Israeli-Palestinian conflict.

Role of International Humanitarian Law during Armed Conflicts

The legality of state conduct during armed conflict falls under International Humanitarian Law, also known as the Law of Armed Conflict. International Humanitarian Law is a branch of international law embodied in treaties and conventions, as well as the generally accepted practices of states known as “customary international law.” Modern International Humanitarian Law emerged in the mid-19^th century when steps were first taken to codify the “laws and customs of war.” Further development occurred in the 20^th century, principally via the four Geneva Conventions of 1949 and their two Additional Protocols of 1977. The 1977 Geneva Convention Additional Protocol I (“AP I”) is the treaty most relevant to the present discussion of Russian attacks on merchant vessels.

The Geneva Convention Additional Protocol I 1977

AP I codifies agreed and accepted limits on the ways in which wars may be fought with the objective of protecting civilians from the dangers of hostilities. Part IV of AP I (Articles 48-60) codifies rules aimed at ensuring that civilians and civilian objects are protected from the effects of hostilities. The key provisions of AP I apply to naval warfare as well as to conflict on land (ICRC, Naval Warfare). Article 49(3) delineates the scope of AP I to “apply to any land, air or sea warfare which may affect the civilian population, individual civilians or civilian objects on land.”

Article 48 titled “Basic rule” outlines the key principle of “distinction”, namely the requirement that parties to any conflict “distinguish between the civilian population and combatants and between civilian objects and military objectives” and “direct their operations only against military objectives.”

Ukraine has been a party to AP I since 1989, when the Soviet Union ratified the Protocol. Russia, also a member since 1989, but withdrew from AP I in 2019. However, the Russian Foreign Ministry stated at the time that its withdrawal would “not affect Russia’s participation in Protocol I, which continues to remain valid.” Russia’s statement appears to acknowledge that AP I is part of customary international law. 

When provisions of a treaty embody customary international law, they are binding obligations on states regardless of whether or not a state is a party to the treaty. Customary international law is cited in Article 38(1)(b) of the Statute of the International Court of Justice (the “ICJ”) which identifies “international custom, as evidence of a general practice accepted as law” as one of the sources of international law. Simply put, customary international law refers to international obligations arising from established state practices, as opposed to obligations that arise from treaties, such as AP I.  The prevailing view is that an international custom will qualify as customary international law if it meets two requirements: a) it must be a consistent and general practice amongst states; and b) states must engage in the practice out of a sense of legal obligation. (Lotus Case, p. 18; Nicaragua Case, para. 207; Gulf of Maine Case, para. 46).

Russia’s acceptance is at the very least indicative that important parts of AP I represent customary international law – a view shared by the U.S. and other states that have not ratified Additional Protocol I. Accordingly, even though Russia is no longer a party to AP I, the key principles of International Humanitarian Law applicable to naval warfare and armed conflicts contained within it, including the obligations to protect civilians and civilian objects from attack, continue to apply to the Russian-Ukrainian war as customary international law. 

Customary International Humanitarian Law

In addition to the principles of customary international law embodied in the AP I, there are other customs and practices of states which have come to be recognized as norms of Customary International Humanitarian Law which are relevant to a discussion of Russia’s targeting of merchant ships. 

In 2005 the International Committee of the Red Cross (ICRC), which has been integral to the development of International Humanitarian Law since it was founded in 1863, published a comprehensive report on customary rules of International Humanitarian Law. The study draws upon international treaties, military manuals, state customs and practices, and other sources to identify 161 rules of Customary International Humanitarian Law. This post makes reference to the rules contained in the ICRC Customary IHL study which, although not legally binding, is considered an authoritative reference as to the applicable international law.

As reflected in Article 48 of the AP I, Customary International Humanitarian Law requires combatants to distinguish between civilian objects and military objectives. Parties to a conflict “must at all times distinguish between civilian objects and military objectives” and attacks “must not be directed against civilian objects” (ICRC, Customary IHL, Rule No. 7) In its Nuclear Weapons Advisory Opinion (paras. 78-79), the ICJ highlighted this principle of distinction as a “cardinal principle” of International Humanitarian Law and an “intransgressible principle of international customary law.”

Customary rules of international law define “military objectives” as objects that “by their nature, location, purpose or use make an effective contribution to military action and whose partial or total destruction, capture or neutralization, in the circumstances ruling at the time, offers a definite military advantage.” (ICRC, Customary IHL, Rule 8) Conversely, “civilian objects” are “all objects that [are] not military objectives” (ICRC, Customary IHL, Rule 9). Civilian objects “are protected against attack, unless and for such time as they are military objectives.” (ICRC, Customary IHL, Rule 10)

Civilians may be considered a legitimate military target only where they are “directly participating” in hostilities. The rules of Customary International Humanitarian Law as to what constitutes “direct participation” in this context is restated in the ICRC, Interpretive Guidance on the Notion of Direct Participation in Hostilities. For a civilian act to qualify, it must meet the following, cumulative, criteria:

1. The civilian act must be likely to either: (i) adversely affect military operations or military capacity; or (ii) inflict death, injury, or destruction on protected persons or objects (threshold of harm); and
2. There must be a direct causal link between the act and the harm likely to result either from that act, or from a coordinated military operation of which that act constitutes an integral part (direct causation); and
3. The act must be specifically designed to directly cause the required threshold of harm in support of a party to the conflict and to the detriment of another (belligerent nexus).

Applied together, the three requirements—threshold of harm, direct causation, and belligerent nexus—allow for an objective distinction to be made between civilian activities that qualify as direct participation in hostilities and those which, although occurring during an armed conflict, are not part of hostilities and therefore do not cause the civilians involved lose protection against direct attack.

A further authoritative source of Customary International Humanitarian Law relevant to any discussion of Russia’s targeting of merchant ships is The San Remo Manual of 1994, which restates international law applicable to armed conflicts at sea and provides a helpful, non-exhaustive, list of examples of conduct which could make merchant vessels, both enemy and neutral, legitimate military targets. The San Remo Manual arose following naval conflicts Falklands/Malvinas War (1982) and the Iran-Iraq War (1980-1988) to provide clarifications to the applicability of the International Humanitarian Law in naval warfare. 

According to Article 60 of the San Remo Manual, the following activities may make enemy merchant vessels into military objectives:

• engaging in belligerent acts on behalf of the enemy, e.g., laying mines, minesweeping, cutting undersea cables and pipelines, engaging in visit and search of neutral merchant vessels or attacking other merchant vessels;
• acting as an auxiliary to an enemy’s armed forces, e.g., carrying troops or replenishing warships;
• being incorporated into or assisting the enemy’s intelligence gathering system, e.g., engaging in reconnaissance, early warning, surveillance, or command, control and communications missions;
• sailing under convoy of enemy warships or military aircraft;
• refusing an order to stop or actively resisting visit, search or capture;
• being armed to an extent that they could inflict damage to a warship; this excludes light individual weapons for the defense of personnel, e.g., against pirates, and purely deflective systems such as chaff ; or
• otherwise making an effective contribution to military action, e.g., carrying military materials

Similarly, Article 67 of the San Remo Manual provides that merchant vessels flying the flag of neutral States may not be attacked unless they:

1. are believed on reasonable grounds to be carrying contraband or breaching a blockade, and after prior warning, they intentionally and clearly refuse to stop, or intentionally and clearly resist visit, search or capture;
2. engage in belligerent acts on behalf of the enemy;
3. act as auxiliaries to the enemy’s armed forces;
4. are incorporated into or assist the enemy s intelligence system;
5. sail under convoy of enemy warships or military aircraft; or
6. otherwise make an effective contribution to the enemy’s military action, e.g., by carrying military materials, and it is not feasible for the attacking forces to first place passengers and crew in a place of safety. Unless circumstances do not permit, they are to be given a warning, so that they can re-route, off-load, or take other precautions.

Merchant vessels may lose protection against direct attack for the duration of each specific act amounting to direct participation in hostilities. That protection is reinstated as soon as participation in hostilities comes to an end (ICRC, Interpretive Guidance on the Notion of Direct Participation in Hostilities).

Despite the extensive customary rules summaries above, in practice, direct participation in hostilities by civilians can lead to confusion and uncertainty in implementing the principle of distinction. To prevent erroneous or arbitrary targeting of civilians who are entitled to protection, customary rules of International Humanitarian Law require combatants to take all feasible precautions to determine if a person is a civilian and if they are directly participating in hostilities (ICRC, Customary IHL, Rules 15-22). In case of doubt, the person must be presumed to be protected against direct attack.

Individual Criminal Responsibility for Targeting Merchant Vessels

Those committing violations of the rules of International Humanitarian Law could potentially face criminal charges before the International Criminal Court (the “ICC”). However, the ICC’s jurisdiction is not unlimited. It can exercise jurisdiction over states that are parties to the ICC Statute or over states that have accepted specifically the Court’s jurisdiction in accordance with Article 12(3) of the ICC Statute, or where the United Nations Security Council has referred the situation to the Court. The Court will have jurisdiction in respect of war crimes committed on the territory of State Parties, or “if the crime was committed on board a vessel or aircraft” where the state of registration of that vessel or aircraft is a State Party or has accepted the Court’s jurisdiction.

Neither Russia nor Ukraine are parties to the ICC. However, Ukraine has accepted the ICC’s jurisdiction for war crimes committed on its territory since November 2013 in accordance with Article 12(3) of the ICC Statute, giving the ICC Court jurisdiction over any war crimes, crimes against humanity, or genocide committed in Ukraine. This acceptance has the effect of extending the ICC’s jurisdiction over any crimes committed with respect to merchant vessels flying the Ukrainian flag or the flag of any existing State Party to the ICC Statute. Any other state whose vessels may have been attacked by Russia can likewise confer jurisdiction on the ICC for these potential war crimes (if they are not already State Parties to the ICC Statute). 

As for the status of the attacks, under Article 8(2)(b)(ii) of the ICC Statute, “[i]ntentionally directing attacks against civilian objects, that is, objects which are not military objectives” constitutes a war crime. Similarly, under Article 8(2)(b)(iv) of the ICC Statute “[i]ntentionally launching an attack in the knowledge that such attack will cause incidental loss of life or injury to civilians or damage to civilian objects or widespread, long-term and severe damage to the natural environment which would be clearly excessive in relation to the concrete and direct overall military advantage anticipated” qualifies as a war crime. 

Given Russia’s declared intention to consider all vessels entering Ukrainian ports as potential military targets, there appears to be well founded basis for Russia’s attacks on merchant vessels being investigated as war crimes under Articles 8(2)(b)(ii) and 8(2)(b)(iv) of the ICC Statute. In the specific case of the “Millennial Spirit,” a chemical tanker, there was an additional risk of serious long-term environmental damage due to chemical leakage providing a potential alternate or additional basis for criminal liability under Article 8(2)(b)(iv) of the ICC Statute.

On March 5, 2024, ICC Pre-Trial Chamber II issued warrants of arrest for two individuals in the context of Russia’s aggression in Ukraine: Russian Armed Forces Lieutenant General Sergei Ivanovich Kobylash, who at the relevant time was the Commander of the Long-Range Aviation of the Aerospace Force, and Russian Navy Admiral Viktor Nikolayevich Sokolov, who at the relevant time was the Commander of the Black Sea Fleet. Based on the Prosecution’s applications of February 2, 2024, Pre-Trial Chamber II considered that there are reasonable grounds to believe that each suspect bears responsibility for the war crime of directing attacks at civilian objects, the war crime of causing excessive incidental harm to civilians or damage to civilian objects, and the crime against humanity of inhumane acts. To date, the ICC Prosecutor has not sought arrest warrants for anyone involved in the attacks on merchant vessels in the Black Sea.

Legality of Attacks on Merchant Vessels under the United Nations Convention on the Law of the Sea

Attacks on merchant vessels may also violate the United Nations Convention on the Law of the Sea (the “UNCLOS”), to which both Russia and Ukraine are parties. 

Pursuant to Article 29 of the UNCLOS, “’warship’ means a ship belonging to the armed forces of a State bearing the external marks distinguishing such ships of its nationality, under the command of an officer duly commissioned by the government of the State and whose name appears in the appropriate service list or its equivalent, and manned by a crew which is under regular armed forces discipline.”  Any vessel not described by the definition above is treated as a civilian vessel.

Article 17 of the UNCLOS grants ships from all states, whether coastal or landlocked, the right of innocent passage through the territorial seas of coastal states. Article 19 of the UNCLOS clarifies that “[p]assage is innocent so long as it is not prejudicial to the peace, good order or security of the coastal State.” Article 25 of the UNCLOS allows a coastal state to “take the necessary steps in its territorial sea to prevent passage which is not innocent;” however, attacking merchant vessels that are in innocent passage is not justified. There is, unsurprisingly, no right at all for states to prevent passage of vessels in the territorial waters of other states.

Accordingly, within its own territorial waters (12 nautical miles from the coastal state’s baseline or low-water mark) interference by Russia with the passage of merchant vessels would be lawful only to prevent passage which was not innocent. Outside its territorial waters and within Ukrainian territorial waters any Russian interference at all with the passage of merchant vessels is likely to contravene Article 17.

Under Article 91(1) of the UNCLOS, “[s]hips have the nationality of the State whose flag they are entitled to fly.” Accordingly, flag states whose merchant vessels have been attacked by Russia may seek redress at the UNCLOS International Tribunal for the Law of the Sea, provided they are State Parties to UNCLOS, or the International Court of Justice (ICJ).

Conclusions on the Legality of Russia’s Attacks on Merchant Vessels under International Law

In light of the key rules of Customary International Humanitarian Law summarized above, there can be no doubt that in undertaking military activities, Russia is obliged to comply with the “intransgressible principle” of distinguishing between civilian objects and military objectives. Russia’s targeting of civilian merchant vessels in the Black Sea could only have been legal in circumstances where the targeted vessels met the cumulative requirements of direct participation in hostilities. In other words, each of the vessels would have become a legitimate military target only if it was engaged in activity designed to adversely affect Russian military operations or to damage protected persons or objects, and then only for the duration of such activity. If circumstances of direct participation were suspected to exist, customary international law obliges Russian commanders to take all feasible precautions to minimize the risk of error. 

In the absence of appropriately verified circumstances of direct participation, the targeting of merchant vessels is a violation of International Humanitarian Law. The 2023 declaration by Russia that it would consider all vessels entering Ukrainian ports as potential military targets appears to stand, therefore, as a statement of intent to violate International Humanitarian Law and therefore commit war crimes.

Intentional direct attacks against civil objects, or intentional attacks in circumstances where it is known that the attack will cause excessive incidental loss of life or injury to civilians or damage to civilian objects can qualify as war crimes under the ICC Statute. Although neither Russia nor Ukraine are State Parties to the ICC Statute, the ICC will have jurisdiction over attacks on Ukrainian flagged vessels by reason of Ukraine’s specific acceptance of the Court’s jurisdiction. Any other state whose vessels may have been attached is likewise able to confer jurisdiction on the ICC to investigate and potentially prosecute the individuals responsible for the attacks.

Finally, any Russian interference with the passage of merchant vessels outside its own territorial waters is likely to contravene Article 17 of UNCLOS. Even within Russia’s Black Sea territorial waters, Russian interference with the passage of merchant vessels would only be permitted to prevent passage which is not innocent. Flag states whose merchant vessels have been attacked may seek redress under UNCLOS or at the ICJ.

Authors: Dr. Gregory Noone and Sindija Bēta, Public International Law & Policy Group, and David Robertson, Konstantine Kopaliani, Katherine Krudys, Jan Frankl, Oksana Diachenko, Mitch Riding, and Delyan Yanev

Photo by Tim Mossholder on Unsplash