In Honor of Yoram Dinstein – The San Remo and the Newport Manuals on the Law of Naval Warfare

by | Apr 23, 2024

Naval Warfare Manuals

Editors’ note: This post is part of a series to honor Professor Yoram Dinstein, who passed away on Saturday February 10, 2024. These posts recognize Professor Dinstein’s work and the significant contribution his scholarship has made to our understanding of international law.

Yoram Dinstein’s outstanding contributions to the jus ad bellum and the jus in bello are well known. Nevertheless, not many will associate him with the law of naval warfare. It may, however, be recalled that Yoram Dinstein provided two important entries to the Encyclopedia of Public International Law (today: Max Planck Encyclopedias of International Law) on “Sea Warfare” and on “Neutrality in Sea Warfare.” Another important article, “The Laws of War at Sea,” was published in the Israel Yearbook on Human Rights, which he had been the editor of. Accordingly, it was but logical that he took part in the entire process (from 1988 until 1994) that eventually resulted in the adoption of the San Remo Manual on International Law Applicable to Armed Conflicts at Sea. In 2019, he became a member of the steering committee that has been tasked with updating the San Remo Manual.

While the process of updating the San Remo Manual is continuing, there were some members of the group of experts who were discontent with the slow pace and with the considerable limitations on modifications of the black letter rules. Therefore, they withdrew from the San Remo process to draft an independent manual, i.e., The Newport Manual on the Law of Naval Warfare. This post identifies some of the main accomplishments of the Newport Manual as compared with the San Remo Manual. Although Yoram Dinstein was not a member of the Newport Manual group, I am confident that he would have approved of it.

The San Remo Manual and the Newport Manual – A Brief Comparison

The San Remo Manual was adopted in 1994. Although it has been widely viewed as reflecting the customary law of naval warfare and although it has had a considerable impact on some national manuals, there was and is general agreement that there are some errors that need to be corrected and that some of its rules may not or no longer be based on State practice and opinio juris. For instance, the category of “auxiliary aircraft” in paragraph 13(k) does not exist. And paragraph 110 on ruses provides that auxiliary vessels “are prohibited from launching an attack whilst flying a false flag,” although auxiliaries are not entitled to exercise belligerent rights, i.e., attacks or prize measures. Moreover, since its adoption 30 years ago, there have been technological developments that—naturally—could not be foreseen in the 1990s and that need to be taken account of. The group of experts tasked with the update of the San Remo Manual will certainly discuss these issues. It is, however, unclear whether, how, and when these issues will be addressed in an updated manual. Therefore, the following sections are designed to highlight how they have been dealt with in the Newport Manual.

Relationship Between jus ad bellum and jus in bello

Probably, the most confusing rules of the San Remo Manual are those of Part I, Section II, on “Armed conflicts and the law of self-defence” (paras. 3 to 6). On the one hand, the law of naval warfare is to “apply equally to all parties to the conflict” (para. 6), on the other hand, the jus ad bellum “principles of necessity and proportionality” are considered to limit the belligerents’ options under the law of naval warfare (paras. 4 and 5). Note that Louise Doswald-Beck, the editor of the San Remo Manual Explanation, in her introduction (p. 68) stated that “the rights of belligerents are affected by the restraints of the law of self-defence and that this will affect the rights of belligerents to make full use of all the methods of naval warfare that the traditional law automatically allowed once a state of war existed.”

These rules, which will most likely no longer be part of the updated San Remo Manual, must be understood against the background of the UK position in the 1980s. It may be recalled that the Total Exclusion Zone (TEZ) established around the Falkland/Malvinas Islands was justified with the right of self-defense, although taken at face value it was but an impermissible “free-fire zone” or “zone of unrestricted warfare” (UN Doc. S/15006 (1982); “United Kingdom Materials on International Law,” 53 British Y.B. Int’l L. 542 (1983); Maritime Operational Zones, p. C-11).

In the announcement of April 28, 1982, the British government declared that “any ship and any aircraft, whether military or civil, which is found within the zone without authority from the Ministry of Defence in London will be regarded as operating in support of the illegal occupation and will therefore be regarded hostile and will be liable to be attacked by British Forces.” At the same time, the British government took the view that the parties of the Iran-Iraq War (1980-1988) were not entitled to visit, search and capture merchant vessels because, according to the British government, the exercise of prize measures was not necessary for the self-defense of either belligerent party (House of Commons, Third Special Report from the Defence Committee (Session 1986-87), The Protection of British Merchant Shipping in the Persian Gulf, p. 91-92 (London 1987)). The Newport Manual, while addressing the relationship between the law of naval warfare and the UN Charter (para. 2.4), fully preserves the principle of equal application of the jus in bello (para. 2.4.3) and, thus, rejects any modification of the law of naval warfare based on the right of individual or collective self-defense.

Of course, both manuals recognize the potential impact of the jus ad bellum on the law of (maritime) neutrality, if the UN Security Council has taken binding decisions under Chapter VII of the UN Charter (San Remo Manual, para. 7-9; Newport Manual, paras. 2.4.2., 11.2.1). The re-emerging discussion on whether neutral States continue to be bound by the obligation of impartiality or whether they may adopt a position of qualified or benevolent neutrality is also reflected in both manuals, albeit in a more nuanced manner in the Newport Manual (San Remo Manual Explanation, para. 13.12; Newport Manual, para. 11.2.2).

Impact of New Technologies

As stated, the drafters of the San Remo Manual could not foresee technological developments since 1994. Those developments relate to unmanned maritime systems, directed energy, and to cyber capabilities, and they are addressed in the Newport Manual (paras. 3.3, 6.8, 8.14 respectively).

During the second session on the update of the San Remo Manual (the Canberra online meeting) it became clear that among the group of experts there was considerable opposition to the inclusion of certain unmanned maritime systems into the category of “warships,” although many navies increasingly make use of them for a variety of purposes. It may be recalled that, under the law of naval warfare, only ships qualifying as warships under the generally recognized definition in Article 29 of the UN Convention on the Law of the Sea (UNCLOS) are entitled to exercise belligerent rights. Therefore, denying unmanned maritime systems the status of warship would result in excluding them from conducting attacks, visit, search, and capture.

It is moot to speculate on the reasons for the opposition by some members of the group of experts. However, it is important to emphasize that the definition of warship does not require the ship to be manned to qualify. Rather, it must be interpreted in light of its historical background, i.e., the 1856 Paris Declaration which, inter alia, prohibits privateering. The object of the Paris Declaration was to eliminate the practice of authorizing private entrepreneurs with the exercise of belligerent rights (i.e., privateering) who regularly employed criminals to serve on their ships. Therefore, the emphasis of the Paris Declaration, of the 1907 Hague Convention VII, and of Article 29 UNCLOS is not on manning but on military discipline. Accordingly, the Newport Manual recognizes the right of every State to designate an unmanned maritime system as a warship (para. 3.3).

The Newport Manual addresses cyber capabilities in the context of the notion of “attack” (section 8.1.4). Cyber operations that are designed to cause, or in fact result in, death, injury, damage, or destruction qualify as attacks that are subject to targeting (and weapons) law. Whereas GPS spoofing will regularly not qualify as an attack, it will, if it is “intended to mislead the ship into mined waters and thus is reasonably expected to damage the ship physically.” This approach is narrower than that of the Tallinn Manual 2.0, but this is acceptable because the law of naval warfare is primarily concerned with platforms at sea or in the air.

In the cyber context, it is important to also consider submarine communication cables which continue to be the backbone of cyberspace. Submarine communication cables reportedly carry approximately 95 percent of international data traffic (n. 62). The San Remo Manual addresses the issue only in the context of high seas areas and of the seabed beyond national jurisdiction and places an obligation on the belligerents to “take care to avoid damage” (para. 37). It is unclear why the San Remo Manual does not deal with that important infrastructure in other sea areas. In contrast, the Newport Manual addresses submarine communication cables extensively and recognizes that they may qualify as lawful targets by nature or use (para. 8.6.8). It also makes clear that it is difficult to ascertain whether civilian cables are used for military purposes by the enemy, and emphasizes that any attack on such cables (as distinguished from other interference, such as eavesdropping) is subject to the rules and principles of targeting law. Economic or commercial losses that are to be expected from damaging or destroying a submarine cable are not considered collateral damage.


Unlike the San Remo Manual, the Newport Manual clearly distinguishes between targeting military objectives at sea and on land (paras. 8.5, 8.6). It provides specific guidance as to the notion of “attack” (para. 8.1), on proportionality (para. 8.8), and on precautions in attack (para. 8.9). However, there are no noticeable differences regarding the classification of vessels and aircraft as lawful targets or the basic principles of targeting law. As regards the latter, however, the Newport Manual does not include proportionality as an independent principle but deals with the issue merely in the context of the prohibition of attacks expected to cause excessive collateral damage (para. 5.5.1).

The San Remo Manual addresses the protection of the natural environment in four rules. These include the protection of “vessels designed or adapted exclusively for responding to pollution incidents in the marine environment” (paras. 47(h), 136(g)). This is certainly a novel approach that is not reflective of customary international law. Accordingly, the Newport Manual does not recognize that category of protected vessels. The same holds true for the San Remo Manual’s rules on the protection of the marine environment. Paragraph 11 is based on Article 194(5) UNCLOS, which is not binding on belligerents. Therefore, paragraph 11 merely encourages the parties to the conflict “to agree that no hostile actions will be conducted” in rare or fragile marine areas.

More problematic is paragraph 44. While it may still be acceptable to advise belligerents to pay due regard to the natural environment—although it is doubtful whether the peacetime standard of “due regard” continues to apply in times of an armed conflict at sea—it is far from settled whether the alleged prohibition on damaging or destroying the natural environment “not justified by military necessity and carried out wantonly” has matured into customary international law. The Newport Manual takes a more cautious approach. After a discussion of Article 35(3) Additional Protocol I and the ENMOD Convention, it limits the respective prohibitions to the States party to the respective treaties thus denying them the status as customary international law (para. 6.3)

Methods and Means of Naval Warfare

Both manuals deal with methods and means of naval warfare in separate chapters. However, there are some important differences. Firstly, the Newport Manual clearly distinguishes between methods and means, with means being closely linked to the notion of attack (para. 6.1). Secondly, naval mines are dealt with in a more nuanced manner. If naval mines are employed for anti-access/area denial purposes, they are a method of naval warfare, whereas mines designed or used to attack a specific target qualify as means of warfare (paras. 6.5, 7.2.3). Thirdly, a naval blockade is not assimilated to an attack as defined in the law of armed conflict. Therefore, paragraph 102(b) of the San Remo Manual, according to which a blockade is prohibited if 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,” is not accepted as reflective of customary international law (para. 7.4.5). Fourthly, the section on maritime operational zones in the Newport Manual better reflects contemporary State practice by also specifying the legitimate purposes such zones may serve (para. 7.2.1).

Classes of Vessels and Their Crews

Unlike the San Remo Manual, the Newport Manual cautiously distinguishes between various classes of vessels, including maritime militia vessels, thus providing clear guidance as to their respective legal status (ch. 3). This also holds true for the criteria that apply in the determination of the enemy or neutral character of merchant vessels (paras. 3.9.2, 3.9.3). These criteria also widen the scope of protection of the crews of merchant vessels. It may be recalled that according to the 1949 Third Geneva Convention, Article 4A(5) only the members of the crews of enemy merchant vessels, not of neutral merchant vessels, enjoy prisoner of war status (unless they benefit from a “more favourable treatment” under Article 6 of the 1907 Hague Convention VI). Moreover, the Newport Manual distinguishes between the masters and officers on the one hand and other crew members on the other hand (ch. 10, annexed table, p. 223-24).

International and Non-International Armed Conflicts at Sea

According to both manuals, the law of naval warfare applies to international armed conflicts (IAC). However, the Newport Manual, again takes a more nuanced approach. Whereas paragraph 1 of the San Remo Manual seems to suggest that the law, including prize law and the law of maritime neutrality, applies “from the moment armed force is used,” the Newport Manual reminds the user that “some States take the position the use of force must be sufficiently intense and of some duration to trigger an IAC” and that “State practice seems to justify the conclusion that mere isolated incidents at sea or in the air might not trigger an IAC even if they result in damage or casualties” (para.

The San Remo Manual as such does not address non-international armed conflicts extending to the sea. The explanations to paragraph 1 merely state: “. . . although the provisions of this Manual are primarily meant to apply to international armed conflicts at sea, this has intentionally not been expressly indicated in paragraph 1 in order not to dissuade the implementation of these rules in non-international armed conflicts involving naval operations” (p. 73). Chapter 12 of the Newport Manual recognizes that the law of naval warfare applies to non-international armed conflicts insofar as the rules protecting victims at sea and on the conduct of hostilities are concerned, thus in principle excluding prize law and the law of maritime neutrality.

The Way Ahead

The process of updating the San Remo Manual continues, with the fourth meeting of the group of experts to take place in Haugesund (Norway), from April 16 to 19, 2024. Because the present author is no longer a member of that group, any prediction on the possible outcome would be mere speculation. As regards the Newport Manual, its first edition published in May 2023 is not final. In May 2024, the editors will discuss possible amendments of the Newport Manual with international stakeholders. There are no black letter rules the amendment of which require the unanimous consent of the drafters. Moreover, the planned regular exchange with international stakeholders in the future guarantees that the Newport Manual will continue to reflect contemporary State practice thus enabling navies to effectively cooperate in combined operations during armed conflicts at sea.


Wolff Heintschel von Heinegg holds the Chair of Public Law, in particular Public International law, European Law and Foreign Constitutional Law at the Europa-Universität Viadrina in Frankfurt (Oder), Germany.





Photo credit: U.S. Navy