1 Introduction

The Ukrainian–Russian armed conflict, which has intensified since February 2022, is a relevant test case to assess the paradigms of continuity and discontinuity explored in this special issue in relation to the law of neutrality. As will be discussed in this paper, this conflict has emphasized how many States have openly engaged in forms of conduct which clearly show discontinuity with traditional views related to the law of neutrality, while others have conversely vindicated a rigid continuity of legal parameters in this area or have avoided to take a clear stance. To some extent, some of the States involved largely lacked a proper engagement with the law of neutrality which has appeared as a hidden legal argument in their positions. Furthermore, attempts have been made to identify legal solutions grounded outside the law of neutrality for justifying current actions, through an approach potentially able to imply the progressive irrelevance of the law of neutrality. This mixture of approaches implies significant challenges in identifying the current state of the art in relation to this branch of law.

This paper will thus address legal challenges related to the law of neutrality in the Ukrainian–Russian armed conflict. In a nutshell the law of neutrality implies specific obligations and rights in the relationship between States parties to an international armed conflict and neutral States.Footnote 1 This legal framework has traditionally been interpreted as implying how the neutral State has a series of obligations towards belligerent parties. In particular, the neutral State must abstain from supporting one party to the international armed conflict, particularly through the provision of war materiel and potentially massive financial assistance, as accompanied by the duties not to tolerate its territory to be used against one of the belligerent parties for warlike purposes and to act in an impartial manner, for instance avoiding to create differences in case the neutral State decides to limit trade relations with belligerent parties. Conversely, neutral States enjoy some rights, in particular the right not to be adversely affected by the conduct of hostilities, the prohibition on belligerent parties entering and using territories and areas belonging to neutral States for carrying out military operations, and the possibility to continue trade relationships with belligerent parties, except in relation to activities that are incompatible with the law of neutrality. The status of neutrality becomes relevant upon the occasion of an international armed conflict and there is no need for a neutral State to adopt a formal declaration or other formal measures to express its stance.

Even if this body of law might appear as a relic of the past—as its written codification is still linked to the 1907 V Hague Convention on land warfare and the 1907 XIII Hague Convention relating to maritime warfare—it is still strongly credited to have legal relevance. As maintained by the International Court of Justice, the ‘principle’ of neutrality is ‘an established part of customary international law’,Footnote 2 a solution confirmed by national judgments and other elements of State practice,Footnote 3 chiefly military manuals,Footnote 4 which still require the application of this set of rules. Furthermore, in recent years academic debates, as complemented by private codifications arranged by international humanitarian law experts,Footnote 5 have confirmed the relevance of this legal regime.

In past decades the major discontinuity in this legal regime could be identified by the emergence of the centralized system of collective security, potentially permitting the United Nations Security Council (UNSC) to adopt binding resolutions under Chapter VII of the UN Charter in order to require Member States to adopt measures interfering with the law of neutrality.Footnote 6 This solution, already discussed at the time of the League of Nations,Footnote 7 could permit States to be released from their obligations under the law of neutrality. However, its proper functioning would require the UNSC to identify the State responsible for a threat or breach of the peace, or an act of aggression, and the adoption of non-military and military enforcement measures against it. In this case Member States would not have the right to maintain a stance of traditional neutrality.Footnote 8 Uncertainty remains as to the admissibility of further derogations from the law of neutrality, as analysed below, particularly in relation to so-called ‘qualified’ neutrality (Sect. 3).

Against this background, the Ukrainian–Russian armed conflict might permit the trends in the law of neutrality and its legal contours to be assessed. First, we will deal with the practice confirming the continuity of this legal regime, exploring positions held by States adhering to firm traditional legal approaches or adopting limited forms of military assistance (Sect. 2). Subsequently we will explore the practice representing a discontinuity regarding the traditional parameters of the law of neutrality, particularly by States endorsing fully-fledged military support to warring parties (Sect. 3). This analysis will also permit a further trend in the law of neutrality to be identified, namely its potential irrelevance, as States’ silenceFootnote 9 aimed at avoiding engaging with this body of law raises questions as to its effectiveness and continued relevance, particularly in light of the potential identification of further legal solutions for justifying such conduct (Sect. 4). In the concluding remarks the potential long-term impact of the current conflict for the law of neutrality will be discussed, particularly the opportunity to depart from its traditional premises to factor ius ad bellum elements into this body of law (Sect. 5).

2 Continuity

The law of neutrality, as interpreted according to traditional approaches, has certainly played a role for some States in the Ukrainian–Russian armed conflict. The most prominent example is provided by Switzerland which has officially reaffirmed its adherence to a strict approach regarding the provision of military materiel. As maintained by the Swiss Federal Council in its highly detailed report on this topic issued in October 2022, ‘[t]he law of neutrality prohibits the direct transmission of war materiel from one’s own military stocks to the parties to a conflict. As a result, Switzerland cannot supply war materiel from its army stocks to either Russia or Ukraine’.Footnote 10

This solution has had reverberating effects for other States, as exemplified by the denial of authorizations to re-export to Ukraine military materiel sold by Switzerland, as illustrated by the 2022 November decision by the Swiss Government to prohibit Germany from re-exporting certain Swiss-made weapons to Ukraine, originally purchased by Germany,Footnote 11 and similar refusals made to Denmark, Spain and the Netherlands in 2023.Footnote 12 Nonetheless, Switzerland has authorized the exportation of functional components for the making of war materiel ‘even if the war materiel manufactured abroad could then reach Ukraine’.Footnote 13 In this respect it is held that ‘[t]he law of neutrality does not regulate this scenario involving international value creation chains’, providing that such components would be less than 50% of the final product.Footnote 14 A strict approach has however been confirmed for non-lethal war materiel as such materials which ‘are classified among goods usable for military purposes’.Footnote 15 Switzerland has also denied the ‘overflight of military aircraft of other States with the aim of providing military support to the parties to the conflict, in particular through the delivery of war materiel’.Footnote 16

To the best of our knowledge, a full engagement with the law of neutrality and a reaffirmation of its legal basis for informing a State’s conduct has however only characterized the position held by Switzerland. Indeed, even if it should be recognized that the majority of States did not adopt any measures of military support in favour of belligerents, including Ukraine, thus practically adopting a position in line with the basic requirements provided by this body of law, it is hard to attribute specific legal value to such conduct. In particular, it could be noted how there was a lack of engagement by such States with the law of neutrality. This could be exemplified in debates held within the UNSC and the United Nations General Assembly (UNGA) where this body of law was not mentioned as the legal framework potentially imposing such conduct, and general concerns were only expressed on risks for the proliferation of the circulation of weapons without framing the abstention to provide military assistance as mandated by the law of neutrality.

Furthermore, States have refrained from using such rules to criticize the conduct of the States providing military assistance to Ukraine. The only exception is obviously provided by Russia. However, for a long period, Russia did not frame its condemnations under the law of neutrality. Apparently, only in a confidential diplomatic note sent to the USA in April 2022, entitled ‘On Russia’s concerns in the context of massive supplies of weapons and military equipment to the Kiev regime’, mentioned by a newspaper and confirmed by Russia, did this latter State ‘accuse[d] the allies of violating “rigorous principles” governing the transfer of weapons to conflict zones’.Footnote 17 In this case, however, it is hard to speculate whether Russia effectively invoked breaches of the law of neutrality, potentially limited by domestic constraints related to the self-qualification of its armed attack against Ukraine as a ‘special military operation’. This label could have indeed made it more complex for Russia to invoke violations of a legal regime pertaining to international armed conflicts.

It took more than a year for Russia to start referring to this body of law in its statements at the UNSC, in order to denounce violations of the law of neutrality. First, on 18th May 2023, Russia claimed how the supply of weapons and the sharing of military intelligence implied that those States had become ‘parties to the armed conflict with Russia, according to the 1907 Hague Convention concerning the Rights and Duties of Neutral Powers in Naval War’.Footnote 18 This statement was quite inaccurate as potential violations of the law of neutrality do not have an impact on the qualification of parties to an armed conflict, an issue regulated by parameters provided by international humanitarian law.Footnote 19

Finally, a lengthy statement was made by Russia at the UNSC in June 2023 where this State addressed potential grounds for justifying the provision of military assistance to Ukraine, maintaining as a preliminary point that ‘international law, including the provisions of the Hague Convention of 1907 and the norms of customary international law, which prohibit such actions by neutral States, are unequivocal’.Footnote 20 In this document, first, Russia reiterated the continuing relevance of the law of neutrality, claiming that ‘our former partners … say that the Hague Convention of 1907 is supposedly terribly outdated. It is very strange to hear that from States whose military agencies are regularly updating and rewriting heavy tomes dedicated to the law and customs of war. These tomes include lengthy sections about the rights and duties of neutral States… The 1907 Hague Convention is an international agreement that remains in force; it has not been abrogated.’ Second, Russia dismissed the possibility to discriminate among belligerent States, mainly based on the technical ground that it was a matter for the UNGA to label Russia as an aggressor rather than the UNSC, also rejecting the ‘qualified’ approach to the law of neutrality. According to Russia,

[a]nother argument is based on branding our country the aggressor, as the General Assembly did… The main issue is that, in principle, the General Assembly is not empowered under the United Nations Charter to determine that an aggression has occurred. Such qualifications are in violation of the provisions of the Charter and are nugatory ab initio. That means that the label of ‘aggressor’ is not a legal qualification… Without legal foundation, everything that has been built on the so-called qualified neutrality argument simply crumbles.

Third, the possibility to invoke legal grounds outside the law of neutrality, namely collective self-defence and countermeasures subsequently explored in Sect. 4, have similarly been dismissed. According to Russia,

[t]he arguments of the Western legal doctrine according to which collective self-defence is supposedly being invoked under Article 51 do not stand up to scrutiny either … we cannot recall the Council being notified of such an invocation, even though, according to the Charter, that should be done immediately… What is even more interesting are the references to alleged countermeasures under international law. As we all know, such measures must meet the criterion of proportionality. But what kind of damage did Russia do to the United States or the European Union that would justify the killing of our citizens with Western weapons…?

This statement is particularly significant being, so far, the only public position expressed by Russia on the continuing relevance of the law of neutrality and its traditional contours in order to pinpoint violations of this body of law. However, Russia embarked more on an academic debate rebutting positions expressed by ‘Western legal doctrine’, analysed below, distinct from the few scholars who have qualified the provision of weapons as a violation of the law of neutrality,Footnote 21 rather than engaging with concrete positions expressed by other States which have largely ignored references to this body of law, as analysed below in Sects. 3 and 4.

Within the parameters of continuity we might eventually include a further scenario, namely the approach adopted by a separate group of States which, conversely, have limited themselves to providing non-lethal materiel, such as military vests and helmets, to Ukraine. This approach has been exemplified by New Zealand’s Prime Minister who maintained how ‘[t]his is the first time New Zealand has provided direct funding to a third party organisation for non-lethal military assistance’ in relation to the provision of body armour, helmets and vests.Footnote 22 A similar approach has been adopted by other States, such as Ireland,Footnote 23 IsraelFootnote 24 and Japan.Footnote 25 Reference could equally be made to South Korea which has only provided non-lethal war materiel,Footnote 26 even if it has recently authorized Polish exports of howitzers to Ukraine which include parts manufactured in South Korea.Footnote 27 Finally, Austria has clearly opposed the sending of lethal war materiel to Ukraine but has provided it with non-lethal materiel such as helmets and flak jackets, and has even authorized the transport of weapons and other military equipment through its territory, including its airspace, through a measure qualified as hardly tenable with the traditional premises of the law of neutrality.Footnote 28

The position adopted by this group of States could be interpreted in two ways. On the one hand, it could be considered how some past similar elements of practice could be recorded where States claimed to be neutral but nonetheless provided non-lethal war materiel.Footnote 29 In this regard, this current practice could confirm this approach, keeping such conduct within the parameters of the continuity of this legal regime, such conduct being finally qualified as admissible and tolerated by the belligerent parties. On the other hand, the practice adopted by such States aimed at only providing non-lethal war materiel to belligerent parties might militate against the emergence of discontinuity in this legal regime, particularly precluding the emergence of the ‘qualified’ exception explored in the subsequent section. Indeed, the law of neutrality might have been interpreted as precluding military support through the provision of lethal war materiel, thus imposing on such States the need to limit their assistance to non-lethal support. However, it is hard to identify clear statements framing such positions within a proper engagement with the law of neutrality.

3 Discontinuity

Even if a complete picture is far from being clear, a few dozen States have conversely provided lethal war materiel to Ukraine, also through non-institutional forms of cooperation such as the Ukraine Defense Contact Group aimed at coordinating support measures through periodic meetings of NATO and non-NATO Member States.Footnote 30 Furthermore, the EU is providing military support to Ukraine through the European Peace Facility (EPF),Footnote 31 which in February 2022, through Council Decision (CFSP) 2002/238, started to be used for providing assistance to Ukraine, including military supplies and lethal war materiel.Footnote 32

These practices have sparked a substantial debate. Based on the law of neutrality, only a significant discontinuity regarding the traditional premises of this legal regime could permit one to admit the provision of lethal war materiel. In particular, reference should be made to concepts such as qualified neutrality, a theory aimed at factoring ius ad bellum elements into this area. This theory admits how neutral States could discriminate between parties to the conflict, not being obliged to maintain strict neutrality towards States which are victims of the unlawful use of armed force against them.Footnote 33 Based on such premises, each State would be entitled to apply a ‘qualified’ neutrality in favour of victims of aggression, including through the provision of lethal war materiel. This solution, based on a decentralized assessment of ius ad bellum elements according to which each State can react to violations of the use of force by not applying the law of neutrality towards the aggressor state, would thus work independently from the undisputed scenario mentioned above according to which a binding resolution of the UNSC under Chapter VII of the UN Charter might require Member States to adopt measures derogating from the law of neutrality.Footnote 34 This latter scenario is however unavailable in the present case due to the veto power potentially exercised by Russia.

This ‘qualified’ exception, whose origins are commonly traced back to the position held by the USA at the time when it was neutral during the early stages of World War II (1939–1941),Footnote 35 has however been explicitly advanced in the past by very few States.Footnote 36 Additionally, it has not gone without criticism by scholars with the consequence that this legal approach, before the Russian-Ukrainian armed conflict, was qualified as having failed to crystallize as customary international law. In particular, based on the lack of a substantial practice confirming this approach, this theory was largely dismissedFootnote 37 maintaining that ‘allegations of derogation of the law of neutrality are, to say the least, premature and that there is no basis for concepts such as “benevolent neutrality” or “non-belligerency”’,Footnote 38 as ‘qualified neutrality is not a part of contemporary international law’.Footnote 39 Apart from the lack of practice, one of the main concerns was related to challenges in clearly identifying, without the formal involvement of the UNSC, the violator of the ius ad bellum as belligerent parties obviously have different views on their legal justifications. This latter scenario could also be present in the current conflict, as exemplified by the claims made by Russia before the UNSC on its alleged exercise of prerogatives provided by Article 51 UN Charter.Footnote 40

Conversely in the case of Ukraine, a substantial number of scholars have endorsed the need to favour discontinuity in this area of law favouring the emergence of a ‘qualified’ neutrality approach,Footnote 41 largely based on the flagrant violation of the UN Charter by Russia, as confirmed by UNGA Resolution ES-11/1,Footnote 42 and the impossibility for the UNSC to exercise its functions due to the veto exercised by one of the warring parties. Based on such premises, it has been maintained that: ‘any application of the traditional law of neutrality and the concomitant equal treatment of the aggressor and the victim of aggression would be tantamount to a declaration of legal and moral bankruptcy’.Footnote 43

Interestingly, some States’ positions appear to echo this solution, without however taking a clear stance in this regard. It is thus hard to identify statements aimed at expressly invoking the ‘qualified’ neutrality exception. Indeed, even if the provision of weapons has been linked with the ongoing aggression carried out by Russia and the individual right of self-defence exercised by Ukraine, an express invocation of a right of qualified neutrality is absent in their statements.

This ambiguous approach could be identified in several statements made in UNSC debates. France maintained that ‘Ukraine has the right to defend itself under Article 51 of the Charter. France, with its partners, has chosen to provide Ukraine with military support to help it to exercise that right.’Footnote 44 Joint statements were expressed by the Baltic and Nordic States, according to whom ‘[u]nder the Charter, Ukraine has an inherent right to self-defence. The Nordic and Baltic States are determined to enhance Ukraine’s military capabilities and to provide all necessary support.’Footnote 45 This is confirmed by Norway which claimed that ‘[o]ther States are entitled to respond positively to Ukraine’s call for assistance in the exercise of its legitimate right to self-defence’.Footnote 46 The USA underlined how ‘the inherent right to individual and collective self-defense is reflected in Article 51 of the Charter… The security assistance, including weapons … is for Ukraine’s self-defense… Ukraine is using those weapons to repel the invading Russian forces’,Footnote 47 recently reiterating how ‘the United States will continue to offer its full support for Ukraine’s self-defense and the principles of the Charter of the United Nations’.Footnote 48 While considering the provision of weapons, the UK affirmed ‘We will continue to support Ukraine in defending itself…, as Ukraine defends itself in accordance with Article 51 of the Charter of the United Nations’.Footnote 49

Interestingly, some UNSC members, even if not directly providing lethal war materiel, have endorsed such actions. Ghana reaffirmed ‘Ukraine’s inherent right to self-defence under customary international law’ and affirmed that ‘[t]here is no prohibition on such action, neither do the rules of international law or the Charter prohibit the supply of conventional weapons to a State under armed attack by another’.Footnote 50 Ireland positively assessed the ‘military support provided by the European Union to help Ukraine exercise its inherent right of self-defence and defend its territorial integrity and sovereignty’.Footnote 51 Indeed, the same EU Council Decision 2022/338 on supplying lethal war materiel to Ukraine emphasizes how ‘[t]he objective of the Assistance Measure is to contribute to strengthening the capabilities and resilience of the Ukrainian Armed Forces to defend the territorial integrity and sovereignty of Ukraine and protect the civilian population against the ongoing military aggression’.Footnote 52

At the domestic level, some positions held in parliaments or in official statements have linked the provision of weapons to the ongoing aggression and the individual right to self-defence for Ukraine. These positions have been expressed by several European States, such as Germany,Footnote 53 Greece,Footnote 54 Italy, where the resolution adopted by Parliament encouraged the Government’s actions,Footnote 55 Luxembourg,Footnote 56 and Romania,Footnote 57 with similar positions echoed in a joint declaration between the UK and Ukraine.Footnote 58 Similarly, US Public Law 117–118 ‘Ukraine Democracy Defense Lend-Lease Act of 2022’, whose title even recalls US legislation providing support to the UK during the early stages of WWII, provided the USA President with the authority ‘to enter into agreements with the Government of Ukraine to lend or lease defense articles to that Government to protect civilian populations in Ukraine from Russian military invasion’.Footnote 59

Before addressing the relevance of such practice and its impact in a potential role in favouring discontinuity regarding this legal regime, a further analysis should take place in relation to an additional scenario raised by this armed conflict, namely the potential irrelevance of this body of law in light of legal solutions grounded outside the law of neutrality.

4 Irrelevance

In order to identify the legal grounds for providing military support to Ukraine, scholars have also referred to further arguments, namely circumstances precluding international wrongful acts. In this regard, lacking any engagement with legal challenges related to the law of neutrality, it could be argued how this body of law would be irrelevant for such positions as solutions outside this legal regime might eventually provide a legal basis for justifying current conduct.

In particular, some scholars have claimed that the provision of weapons to Ukraine could be justified as a form of collective self-defence under Article 51 of the UN Charter.Footnote 60 This approach is based on the a maiore ad minus argument, maintaining that Article 51, legitimizing collective self-defence against the State responsible for an armed attack, can implicitly justify a right to resort to less intrusive measures, such as the provision of weapons to the State which is the victim of the aggression.

From our perspective, this conceptualization might have some shortcomings. First, on a procedural level, we cannot discover any formal communication by the States involved under Article 51(2) to the UNSC. Even if compliance with this requirement is not mandatory for resorting to self-defence, the current approach is striking in light of the numerous instances in which the same States providing military materiel to Ukraine have recently informed the Council of actions which qualify as resorting to individual or collective self-defence in other contexts.Footnote 61 Second, the a maiore ad minus argument does not seem to be consistent with the purpose of Article 51 aimed at creating an express exemption from the specific prohibition on using force as imposed by the Charter itself under Article 2(4). In this respect scholars have maintained that ‘[i]t is nevertheless doubtful whether the right to get involved in an armed conflict by reference to the right of collective self-defense justifies the conclusion that, de majore ad minus, non-participating States are also free to openly discriminate against a party to an international armed conflict’ for the purposes of the law of neutrality.Footnote 62 Doubts only increase when considering the lack of past practice supporting this approach.Footnote 63

Third, it must be noted how in the current scenario, States providing military support to Ukraine have not claimed to be acting in collective self-defence. The only exception could be identified in the statements made before the UNSC by Albania, where, in relation to arms transfers to Ukraine, the point was made that ‘there is a clear provision agreed by everyone on how to help victims, and Article 51 of the Charter provides the legal basis for individual States to offer whatever assistance to a country exercising its inherent right to self-defence’,Footnote 64 while a less clear reference could be found in the position maintained by Poland according to which ‘[a]ssisting such a country is not only admissible, but legally substantiated and morally right… Poland is proud to be a part of the world’s collective self-defence against the trespasser trampling on the most fundamental principles of the United Nations Charter.’Footnote 65 Conversely, other States have avoided any reference to this notion or have denied its relevance. This point was made clear by the German State Secretary in her statement on the supply of weapons to Ukraine according to which ‘[t]his lawful assistance does not pass the threshold of an exercise of the right of collective self-defence’.Footnote 66

Finally, the qualification of such activities as lawful countermeasures should be explored.Footnote 67 In particular, taking into account that the prohibition of aggression implies erga omnes obligations, as maintained by the ICJ in the Barcelona Traction case,Footnote 68 an argument could be made that States other than the injured State could disregard obligations pertaining to the law of neutrality as a legal response to the Russian aggression. Even if the provision of military assistance interfered with the duties imposed by the law of neutrality, the unlawful aggression would deny the aggressor State the possibility of exercising its prerogatives under this body of law. The conduct of third States could thus be identified as a countermeasure in reaction to the unlawful act committed by the aggressor State. Even if doubts are notoriously present regarding third States’ countermeasures,Footnote 69 this option cannot be entirely ruled out. Some of the conditions provided for countermeasures by Articles 51–52 of the ILC Draft Articles on Responsibility of States for Internationally Wrongful Acts could be fulfilled in the current scenario, considering how military assistance is aimed at halting the ongoing aggression, and could be qualified as being proportionate. Furthermore, countermeasures might also explain the approaches adopted by States, ranging from the provision of lethal or non-lethal war materiel to abstention from such acts. As States are not mandated by international law to respond to violations of erga omnes obligations, their inaction or different forms of support provided to Ukraine could be explained as being in line with the latitude of behaviours that international law can accommodate in such cases. The fact remains, however, that no clear statements could be identified in States’ practice supporting the adoption of this legal argument.

Reference to countermeasures seems to be a sounder solution than the qualification of the described measures as collective self-defence. It might also better respond to doubts related to the current existence of a ‘qualified’ neutrality exemption, being that this latter solution is a legal approach which, before the Russian-Ukrainian armed conflict, had failed to crystallize and, in the current context, has not openly been vindicated by the States concerned. However, the main disadvantage of this theory is that it is dependent on admitting recourse to countermeasures for States other than the injured State, a solution which is far from being accepted. Even for this hypothesis, however, we must note the absence of explicit references in State practice, making it more of a scholarly construct than a position grounded on the behaviour of States.

5 The (Uncertain) Current State of the Art on the Law of Neutrality

The analysis of State practice carried out in this article shows that the law of neutrality has played a marginal role in the justification for or the criticism of measures adopted in support of Ukraine in the Russian-Ukrainian war. Limited references to the body of law makes it complex to identify any clear trends on the continuity, discontinuity or even irrelevance of this body of law.

That being said, the continuity approach has some merits as it freezes the law of neutrality to its traditional parameters providing a clear legal framework whose rationale could be linked with the need to avoid the spreading of armed conflicts, keeping economic business as usual, minimizing the economic disruption of war, finally permitting a neutral country ‘to assert its sovereignty notwithstanding being torn between two rival blocs’Footnote 70 and avoiding neutral States having to suffer ‘pressure by belligerents to adopt their views on whether their use of force is justified, which would result for economic and geopolitical reasons in double standards’.Footnote 71 Whether or not this rationale could still be recognized for some States that have traditionally adopted a policy of neutrality and have continued to claim its relevance also based on limits embodied in domestic law and policies, this solution might finally risk substantially favouring great political and military powers. Such actors can indeed be able to disregard basic principles of the international legal system, such as the prohibition on the use of force, without suffering adverse consequences and furthermore being able to prevent the party which is being attacked from obtaining military support from other States due to the limitations imposed by the law of neutrality. Furthermore, support for a continuity approach could be further put into question in light of the unclear position held by the large majority of States not taking a side in the current conflict which, regardless of not providing any form of military support or limiting their assistance to the provision of non-lethal materiel, have avoided to clearly link their conduct to limits imposed by this branch of law.

In the face of the overt Russian aggression with no prospects of UNSC action, a number of States have conversely endorsed a discontinuity paradigm regarding the law of neutrality by openly providing military assistance to the party which is being attacked, essentially ignoring the potential limits imposed by this branch of law. In this manner such States have implicitly considered a violation of the ius ad bellum to trump neutrality. However, the question of which legal argument could justify the choice of supporting one of the belligerents has not been clearly addressed, even if ample emphasis has been placed on the violation of the ius ad bellum and the attacked State’s right to self-defence.

On the one hand, it could be argued how current practice militates for a decentralized assessment of the legality of the use of force by States when the UN collective security system is blocked and the law of neutrality retains, formally, its applicability. This possibility might allow a State, for the purposes of the law of neutrality, to discriminate against the aggressor, thus favouring the emergence of a ‘qualified’ exception to this legal regime favouring the possibility to provide military assistance to the State which is the victim of aggression. Decentralized assessments of the use of force might however bring the risk of favouring the emergence of cacophonic views on the legal qualification of breaches of the ius ad bellum. In the Russian-Ukrainian armed conflict resolution ES-11/1 adopted by the overall majority of the UNGA condemning the aggression in light of the impasse experienced at the UNSC has therefore also been instrumental in reinforcing the position held by States providing military support to Ukraine, even if the ‘qualified’ approach should not be linked, for its functioning, to the need to obtain endorsements from the UNGA.

On the other hand, however, a major challenge in framing current conduct within paradigms provided by the law of neutrality is provided by the self-restraint attitude of the States concerned which have commonly avoided engaging with the law of neutrality, eventually invoking current events as a game changer in this area of law. As mentioned above, in the Russian-Ukrainian armed conflict States providing military support to Ukraine have failed to properly advocate for discontinuity in this legal regime in order to crystallize the ‘qualified’ exception. As recently summarized, ‘[a] right of qualified neutrality is totally absent in their statements. As a result, this practice is totally devoid of opinio juris in support of a customary law right of qualified neutrality. This appears to leave the traditional law of neutrality valid and the admissibility of qualified neutrality a subject of continuing academic debate.’Footnote 72 Such States have also implicitly endorsed the legal irrelevance of the law of neutrality either claiming the application of further legal arguments under international law for justifying their conduct, outside the solutions provided by the law of neutrality or, basically, failing to provide clear legal reasoning for their conduct in light of this legal regime.

The silence by the States in question concerning their legal approaches might have different reasonings. On the one hand, the uncertain legal character of the most promising arguments to legitimize assistance, namely the ‘qualified’ exception and the invocation of individual countermeasures to disregard the obligations of neutrality, may have prevented States from convincingly adopting them. On the other hand, the political-legal interest in avoiding arguments which could be used in the future by other States to provide military support to belligerents even when faced with less manifest violations of the ius ad bellum could have been a main constraint. As already experienced with the reverse effect of theories related to remedial secession and humanitarian interventions, originally advocated by some Western States and scholars and now part of Russian lawfare and misused for its aggressive conduct, the risk of providing arguments to be exploited by other States in the future could have been qualified as a more compelling argument than elaborating a solid theoretical legal framework for such military support.

Nonetheless, the Russian-Ukrainian conflict shows that a significant number of States are unwilling to condone a blatant violation of the rules on the use of force confirming, in this area too, the trend favouring the enforcement of the common interests of the international community through the action of third States.Footnote 73 The thesis that in case of flagrant violations of the ius ad bellum it would be possible to lift the traditional neutrality obligation of third States not to deliver lethal war materiel to the benefit of a State exercising its right of individual self-defence thus seems to be gathering momentum. This approach could be endorsed as it might permit ius ad bellum concerns to be factored into this legal regime. Its goal would be to avoid retaining an international legal order where violations of its basic principles, such as the prohibition on the use of force, could take advantage both of legal arguments related to the law of neutrality elaborated at the time in which ius ad bellum limits were not present and by privileged political positions imposing a deadlock position for the UNSC’s collective security system.

This approach might finally imply that ‘the law of neutrality … appears destined to find still less room for application, if not to vanish entirely through obsolescence’.Footnote 74 However, this trend should be accompanied by some caveats. Indeed, advocating the blanket disappearance of the law of neutrality, apart from being complex in light of its continuing re-emergence in State practice, could have a backlash effect, permitting States to support any belligerent party, including the one which is responsible for violations of ius ad bellum. Conversely, endorsing exceptions to this legal regime, such as the ‘qualified’ neutrality, or eventually the possibility to admit an individual reaction to the violation of the erga omnes obligation enshrined in the prohibition on the use of force, might still permit some legal limits to be retained. In particular, the acceptance of such theories would still permit the avoidance of legitimizing the provision of military support to the aggressor State, as has apparently been arranged in the shadows by some States which support Russia. Indeed, traditional limits related to the law of neutrality would still apply, finally prohibiting other States from providing support for the State responsible for flagrant violations of the rule prohibiting the use of force in international relations.Footnote 75