The Future Law of Neutrality

by | Jul 19, 2022

Future of Neutrality

Editor’s note: The following post highlights a subject addressed in the Lieber Studies volume The Future Law of Armed Conflict, which was published 27 May 2022. For a general introduction to this volume, see Professor Matt Waxman’s introductory post.


Months into the Russia-Ukraine war that began on February 24, many States cautiously, yet gradually, ramped up military support to help Ukrainian people defend themselves. Mounting external support took various forms from intelligence sharing to financial assistance, supply of weapons, and military equipment. The involvement of third parties in the conflict through such support activities has had various legal implications for their neutral status, as well as associated rights and obligations under international law.

It is arguable that unneutral services are justifiable in light of Russia’s open aggression and an overwhelming amount of condemnation against it, as Wolff Heintschel von Heinegg posited in his earlier post. However, many States such as India and Southeast Asian countries remain uneasy about the idea of qualified neutrality. Switzerland is struggling in reconciling its willingness to help Ukraine with its status as a permanent neutral State. And those who support Ukraine are equally walking on a tightrope, as Michael N. Schmitt discussed, between a neutral Good Samaritan or a charlatan foe.

It is not my intention to assess the legality of each support activity under the traditional law of neutrality. Instead, this post considers these activities as indications of evolving practice among States and shows how the boundaries of neutrality law are shifting. Of the four scenarios that I envisaged to unfold in the Future Law of Armed Conflict, the recent State practice appears to be charted into the realm of “benevolent” neutrality, where non-belligerent States find little incentive to strictly adhere to the traditional law of neutrality. A significant factor at play is technological difficulties in restricting and intercepting belligerent access to neutral support and participation in hostile activities. This development has the potential to reduce the role that the law of neutrality plays in regulating the relationship between neutral States and belligerent parties.

Neutral Obligations under the Traditional Law of Neutrality

The traditional law of neutrality was developed to enable non-belligerent States to maintain peaceful relations with belligerent parties involved in armed conflict and continue trading without participating in hostilities. As such, neutral States have an obligation to abstain from providing war-related goods and services to belligerent parties (§ However, this neutral obligation was qualified in three respects when these rules were codified in 1907 under Hague Convention V regarding neutrality in land warfare and Hague Convention XIII regarding neutrality in naval warfare.

First, the obligation of abstention is a specific one, applying to the provision of “munitions of war or supplies” (Article 2 and Article 5 of Hague Convention V) and “warships, ammunition, or war material” (Article 6 of Hague Convention XIII) or associated services such as forming corps of combatants on its territory (Article 4 of Hague Convention V) and arming vessels within its jurisdiction (Article 8 of Hague Convention XIII). This means that under general international law other types of support, such as financial assistance or the provision of goods and services that are unrelated to the conduct of hostilities, fall outside of neutral obligations (cf. Article 16(2) of Havana Convention on Maritime Neutrality). For example, Switzerland has provided humanitarian support to the victims of the war in Ukraine, while Japan pledged a total of $600 million in financial assistance.

Second, neutral States are not required to prevent their nationals from rendering assistance outside their territory. The freedom of commercial trade has been preserved under the traditional law of neutrality, allowing private individuals and companies to export or transport weapons and military equipment on behalf of one or the other of the belligerent parties (Article 7 of Hague Convention V; Article 7 of Hague Convention XIII). This also means that neutral States are not in breach of their neutral obligations by allowing their nationals to voluntarily join a belligerent’s armed forces, such as the International Legion for the Defense of Ukraine, as long as they are not involved in recruitment on their own territory (Article 4 and Article 6 of Hague Convention V). As Nicholas Tsagourias discussed, this exemption would also apply to those individuals who offered their services to the IT Army online.

Third, there is no obligation to prevent the belligerent use of communication stations or apparatus, such as radio-telegraphic stations and telephone cables, established before the commencement of hostilities if these are not used for purely military purposes or if these have been opened for public use (Article 8 of Hague Convention V). A majority of experts who engaged in the drafting of Tallinn Manual 2.0 considered that this exception would extend to cyber communication systems as well (rule 151, para. 4). SpaceX’s Starlink satellite constellation is also likely to qualify under this exception, however, as Timothy Goines and his co-authors pointed out, the belligerent use of such communication infrastructure would convert its enabling assets, such as computer servers and satellites, into legitimate military targets.

Neutral States may also take liberty in imposing further restrictions and prohibitions, but when they do, restrictive measures must be adopted in an impartial and non-discriminatory manner toward all the belligerents (Article 9 of Hague Convention V; Article 9 of Hague Convention XIII). This does not mean that restrictive measures must have equal effect upon the belligerents, nor do they have to be intended as such. Belligerent forces are entitled to exercise repressive measures against neutral subjects engaging in hostile assistance, to which neutral States must acquiesce (Article 17 of Hague Convention V).

The imposition of unilateral sanctions against Russia, as well as weapons export and intelligence sharing in support of Ukraine, may appear to run contrary to these neutral obligations. So, what does this recent practice mean for the future development of neutrality law?

Weapons Export

The government authorization for the export of weapons and military equipment is a clear example of unneutral support. When the Lend-Lease Act was enacted in 1941 to facilitate arms supply to Great Britain and other countries, it triggered concerns that it would permit departure from neutral obligations under international law. As Quincy Wright observed at that time, the Act constituted “the first legislative endorsement since the Napoleonic period” of the abandonment of impartiality in the interest of American defense (p. 313). Eighty-one years later, the U.S. Congress passed the Ukraine Democracy Defense Lend-Lease Act of 2022, authorizing the Biden administration to lend or lease military equipment to Ukraine and other Eastern European countries impacted by Russia’s invasion of Ukraine.

The official endorsement of arms export in support of Ukraine indicates a shift in State practice relevant to the law of neutrality. This shift is taking place due to the geopolitical situation surrounding the Russia-Ukraine war. An important geopolitical factor is that Russia, as the disadvantaged belligerent due to this unneutral assistance, is not in a position to enforce its belligerent rights against neutral States. There are various means to enforce belligerent rights against unneutral assistance, such as capture of neutral merchant vessels carrying contraband. However, Russia has not issued contraband lists to restrict shipments to Ukraine, presumably because it has characterized the engagement in Ukraine as a “special military operation.” As an alternative, the requirement may be satisfied by a listing of exempt goods (§7.4.1), yet, Russia has been blocking neutral trade entirely.

It comes as no surprise that some States are inclined to lend support to a politically, economically or ideologically favored belligerent against another. Indeed, the past practices suggest that States have tried to circumvent or abdicate neutral obligations based on the doctrine of “non-belligerency” or “qualified neutrality.” As Heintschel von Heinegg observed, such practices on the part of some neutral States deviating from the strict rules of neutrality alone are not sufficient as evidence of a corresponding change in the law of neutrality (pp. 553-6). However, Russia’s unwillingness to take remedial measures (other than targeting imported weapons or jamming satellites in the conduct of hostilities), even when there are means at its disposal to enforce belligerent rights in accordance with the traditional law of neutrality, could be indicative of a change in legal considerations.

The current legal landscape is indeed significantly different to the one in which the traditional law of neutrality was developed. As I discussed elsewhere, contemporary international law allows neutral States to invoke the right of collective self-defense as a justification for violations of neutral obligations by supporting one of the belligerent parties (pp. 133-4). This means that even without being part of NATO, Ukraine has the inherent right to request military intervention by other States to help defend themselves, and other States are entitled to provide support in response to such a request. Self-defense justifies not only a use of force which is otherwise prohibited under customary international law but also non-performance of obligations associated with it as a “circumstance precluding wrongfulness” under the law of State responsibility (Article 21 of Articles on State Responsibility). As Michael N. Schmitt has explained, a State would not necessarily lose neutral status by providing unneutral support in the exercise of the right of collective self-defense.

The shift toward “benevolent neutrality” appears to be further facilitated due to practical difficulties in controlling or challenging the provision of support. When the traditional law of neutrality was developed, the primary means of transport was shipping and belligerent parties deployed naval forces to stem the flow of arms trade through maritime routes. In modern days, by contrast, the supply of weapons and military equipment can be airlifted or, with the use of 3D printing, can be locally manufactured through the transmission of necessary data. This trend is likely to continue, with a greater investment in and use of smaller, scalable, and maneuverable unmanned platforms which have proven to be effective against conventional instruments of war. The Russia-Ukraine conflict has demonstrated that neutral States would find little constraint in providing unneutral support when there is no feasible means to detect and intercept such transfer.

Intelligence Sharing

The primary focus of the neutrality law has been the restriction of transgression by a physical act, such as the provision of personnel and arms in support of hostile activities or the belligerent use of neutral territory. In modern conflicts, as has been proven in the Russia-Ukraine war, battlefield intelligence can be equally significant in determining the outcome of battlefield engagement. The United States and NATO allies have reportedly been sharing battlefield intelligence with Ukraine, although the fidelity of information shared and the role it plays in the Ukrainian military’s targeting decisions are uncertain. Does this practice have any implications for the law of neutrality?

As emphasized earlier, the neutral obligation of abstention is limited to the provision of war-related goods and services. The question is therefore whether intelligence sharing qualifies as a war-related service that is prohibited under the law of neutrality. The exemption from neutral obligations pertaining to communication stations and apparatus could arguably include the transmission of messages through those facilities. However, the U.S. Department of Defense Law of War Manual adopts the position that this “does not imply that the neutral State may use such facilities or permit their use to lend assistance to the belligerents on one side only.” (§ A similar view is expressed in the Commander’s Handbook on the Law of Naval Operations, stating that “Any transmission to an opposing belligerent of information concerning military operations or military forces is inconsistent with the neutral duties of abstention and impartiality and renders the neutral vessel or aircraft liable to capture or destruction” (§7.8).

However, whether the prohibition of intelligence sharing has been established as a neutral obligation under customary international law is far from certain. Extensive research conducted in this area by Heintschel von Heinegg found that State practice regarding such unneutral assistance and its consequences was far from uniform (pp. 319-21), noting that the transmission of information was equated to the carriage of contraband (fn. 218). The carriage of contraband by neutral merchant vessels was liable to seizure and the condemnation of the goods, but engaging in contraband trade itself was not considered as a violation of international law. As explained above, neutral States are under no obligation to prohibit such a trade. This finding indicates that while the belligerent right to prevent neutral vessels from transmitting information for the adversary is well established, the corresponding neutral obligation is not.

At any rate, the applicability of neutral obligations to the transmission of information in the past was premised upon the fact that there was practical means to detect and seize it due to the physical form it took, such as a letter or a telegram. Modern technological advances have enabled belligerents to seek support from other States by various non-tangible means, such as the transmission of data and imagery through computer networks. Such non-tangible support is difficult to detect and intercept, which would pose practical challenges to the enforcement of belligerent rights if neutral obligations were to extend to the transmission of information in this digital era.

The relevant question, as Marko Milanovic correctly identified, is rather whether the sharing of battlefield intelligence makes the supporting State a participant in the international armed conflict between Russia and Ukraine. However, as Michael N. Schmitt discussed in an earlier post, this is an issue of conflict classification and a mere breach of neutral obligation does not bring a supporting State into the conflict as a belligerent party. Indeed, a State may lose its neutral status even without violating neutral obligations if the support is integral to the specific conduct of hostilities engaged by a belligerent party. This determination, as I discussed elsewhere, is dependent upon a factual assessment, taking into account various factors such as the domestic policies of the State, the materiality of a breach, and the nature of the assistance relative to the act of hostilities (fn. 118).

Concluding Thoughts

The ongoing conflict in Ukraine has provided some insight as to how non-belligerent States might interact with belligerent parties in the modern environment of warfare and how that might shape the boundaries of neutrality law in the future. Various technological advances have transformed the circumstances in which the law of neutrality operates, compared to the time when it was developed and codified. The ability to supply arms and share battlefield intelligence though interconnected infrastructure has the potential to undermine the fundamental premise upon which the entire legal regime was built.

Combined with this technological factor, the involvement of great powers in support of Ukraine has indicated that modern neutrality law might be emerging in a “benevolent” form, where third parties see little constraint in providing unneutral support. This outlook is further reinforced as a result of deep decoupling of Russia from Western economies through the imposition of sanctions, which has reduced the need to maintain trade relations with Russia and hence to strictly adhere to traditional neutrality rules.

Nevertheless, this event alone does not transform the modern law of neutrality, nor does it determine the course of its development. A more frequent involvement of great powers in international armed conflicts as belligerent parties may shift the pattern of practice in a different direction as they take advantage of unneutral assistance without being detected by the adversary. The law of neutrality will then become “apologetic” in that the legal position of neutral States is submissive to subjective interpretation based on their political interests. Alternatively, with further advances in technology, belligerent parties may acquire technological means to detect and intercept the non-tangible means of support, which will enable them to exercise their belligerent rights against neutral States and their subjects.

The chapter I contributed to the Future Law of Armed Conflict maps out four different scenarios in which the future law of neutrality might emerge in a particular form. As expected, the Russia-Ukraine war has demonstrated that the actual reality is far more complex than the simplified scenarios that were developed in the chapter, involving mixed reactions among non-belligerent States. But it has also made clear that the law of neutrality will remain relevant for legal considerations, one way or another, as long as the United Nations Security Council continues to be stymied.


Hitoshi Nasu is a Professor of Law in the Department of Law at the United States Military Academy.



Photo credit: Senior Airman Thomas Cox, U.S. Air National Guard