On May 7, three uncrewed aerial vehicles (UAVs or drones) crossed into Latvia from Russia. One exploded at an oil storage facility 40 KM from the Russian border, damaging empty oil tanks and sparking a small fire. The second crashed into a field, and the third flew into and then out of Latvia’s airspace. Latvia issued UAV alerts along the Russian border and restricted flights in its airspace, while French military aircraft participating in NATO’s Baltic Air Policing mission responded to the area. The Latvian Ministry of Foreign Affairs summoned the Russian chargé d’affaires and delivered a formal protest. Three days later, the Ukrainian Foreign Minister announced that “[i]nvestigations proved that this was the result of Russian electronic warfare deliberately diverting Ukrainian drones from their targets in Russia.”
This is not the first time Russia has apparently diverted Ukrainian UAVs into the Baltic States. A series of similar UAV incursions occurred in March. That month, a Ukrainian UAV crashed in Lithuania after veering off course during an attack on Russian oil infrastructure. Other Ukrainian UAVs entered Estonian and Latvian airspace from Russia, with one striking the chimney of an Estonian power station and another crashing in Latvia.
These penetrations of the Baltic States’ airspace by Ukrainian UAVs, including the most recent ones, are widely attributed to Russia’s use of electronic warfare (EW) countermeasures (in this context, we use countermeasures in the military, not legal, sense to mean devices or techniques that impair enemy operational effectiveness, DoD Dictionary). However, some doubt remains as to whether the intrusions and resulting damage were deliberate, as the Ukrainian Foreign Minister suggests, or an unintended byproduct of the Russian countermeasures.
Most reports suggest that Russia employed Global Navigation Satellite System (GNSS) spoofing techniques. Spoofing, commonly used in the Russia-Ukraine war, involves transmitters deliberately broadcasting fake signals that mislead the UAV to “accept incorrect coordinates, resulting in navigation failure, loss of control, or forced landing in enemy territory.” In some cases, it can even be used to redirect UAVs to specific coordinates.
Another possibility is that Russia employed jamming, a technique that degrades or blocks satellite navigation signals, causing the system to switch to inertial navigation or crash. While spoofing can intentionally redirect the UAVs, jamming only blocks signals. Thus, the effects of jamming are less controllable. For instance, if the UAV is equipped with AI capabilities, as is now frequently the case, it might be able to continue attacking targets autonomously, even if jamming disrupts communication with its operator. Indeed, some commentators have suggested that the impact at the Latvian oil terminal points to the possible use of AI, as the site is Accordingly, recent incursions of UAVs into Latvia could conceivably have resulted from Russian jamming of Ukrainian UAVs, which forced them to rely on onboard AI systems that misidentified the visually similar Latvian oil terminal as a Russian oil facility, even though neither the jamming nor the AI targeting logic was intended to direct attacks against Latvian objects.
These events continue to raise concerns in the Baltic nations, and NATO more broadly, over preparedness (or a lack thereof) for countering Russian UAV attacks. Indeed, the May incident, following on the heels of the earlier ones, has led to the resignation of both the Latvian Defense Minister and, after the collapse of her governing coalition, the Prime Minister.
Setting aside the political and security issues, as well as the broader legal issue of Russia’s self-evidently unlawful use of force against Ukraine under the jus ad bellum since 2014, this article examines the incidents from an international law perspective. In doing so, we consider two possibilities — that the diversion was intentional and, alternatively, that the penetration of NATO airspace was the unintended result of Russian EW defensive countermeasures. We first address the law of State responsibility, which provides the normative framework within which any violations may have occurred (the “secondary rules” of international law). Then, we survey the possible violations themselves (the “primary” rules of international law).
The critical issue that emerges from this analysis is intent, or a lack thereof, regarding the effects of the EW measures on the cross-cutting legal issues of State responsibility and violations of international law. And more broadly, the incidents illustrate the inherent normative tension during an international armed conflict between the need for belligerents to be able to effectively engage in hostilities and the imperative of shielding neutrals from being affected by those hostilities to the extent possible.
State Responsibility for the Airspace Incursions
Before turning to possible Russian violations, it is necessary to address questions of State responsibility. Two are considered here: 1) the general conditions precedent to a State’s actions, such as the use of EW against the UAVs, being unlawful; and 2) the circumstances in which any wrongfulness on Russia’s part may have been “precluded” as a matter of law.
Internationally Wrongful Acts: Conduct is “internationally wrongful” (unlawful) when it is “attributable to the State under international law” and that attributable conduct “constitutes a breach of an international obligation of the State” (Articles on State Responsibility, art. 2). The first requirement is satisfied, inter alia, whenever the conduct is that of an “organ” of the State (ASR, art. 4; Restatement, Third, Foreign Relations, § 207).
In these incidents, the GNSS spoofing or jamming operations were almost certainly carried out by units of the Russian armed forces, the paradigmatic example of a State organ. If Russia acted deliberately, the acts are obviously attributable to Russia. But even if the consequences were not intended, for instance, because they resulted from the interaction of EW measures and the UAV’s existing AI capabilities, the effects would not have occurred but for Russian actions. They would still be attributable to Russia. As an aside, the fact that the UAVs that penetrated the airspace of the Baltic States were Ukrainian rather than Russian is legally irrelevant.
Having established attribution, the next question is whether Russia’s actions breached any obligations owed to the Baltic States, including the duty to respect the sovereignty of other States, the prohibition on the use of force, and the obligation to respect the inviolability of neutral territory, each of which we discuss below. That inquiry turns on the content of the relevant primary rule. This raises the further question of whether Russia intended the intrusions and the resulting damage.
Intent is legally relevant only if the primary rule includes it as an element of breach. Thus, whether Russia deliberately meant for its EW measures to redirect Ukrainian UAVs into Baltic airspace or toward objects in the Baltic States matters only for those obligations that require such a mental element, a matter discussed below with regard to the individual rules. Where the primary rule contains no intent condition, a lack of intent does not preclude responsibility. As the International Law Commission explained in its commentary to Article 2 of the Articles on State Responsibility, absent such a requirement, “it is only the act of a State that matters, independently of any intention.”
Circumstances Precluding Wrongfulness: In assessing Russia’s potential responsibility for the UAV incursions, it must also be determined whether there are any “circumstances precluding wrongfulness” that would, despite satisfaction of the elements of a breach, nevertheless render the Russian actions lawful. Such circumstances, found in customary international law, are restated in Chapter V of the Articles on State Responsibility. Three merit mention here – force majeure, necessity, and self-defense – though none are availing.
Force majeure applies upon “the occurrence of an irresistible force or of an unforeseen event, beyond the control of the State, making it materially impossible in the circumstances to perform the obligation,” in these cases, the Ukrainian UAV attacks (ASR, art. 23(1)). However, if “the situation of force majeure is due, either alone or in combination with other factors, to the conduct of the State invoking it,” there is no preclusion of wrongfulness (art. 23(2)). As Russia’s EW actions contributed to the airspace violations and damage, force majeure is unavailable.
A second potentially relevant ground for precluding the wrongfulness of an act is “necessity.” It applies when an “essential interest” of the State is facing “grave and imminent peril” and breaching an obligation owed to another State, such as respect for its sovereignty, is the only way to avoid the peril (ASR, art. 25(1)(a)). However, necessity does not preclude wrongfulness where the act “seriously impair[s] an essential interest of the State or States towards which the obligation exists” (ASR, art. 25(1)(b)). Causing armed UAVs to enter the airspace of other States that, in some cases, results in physical damage, plainly impairs their security interests. The essentiality of those interests was demonstrated by the resignations of the Latvian Defense and Prime Ministers following the May incident.
Moreover, necessity is unavailable as a circumstance precluding wrongfulness when the State concerned “has contributed to the situation of necessity” (ASR, art. 25(1)(b)). Russia’s ongoing unlawful armed attack against Ukraine (see UN Charter, art. 2(4)), which triggered Ukraine’s right to self-defense, therefore bars Russia from invoking necessity as a basis for its EW countermeasures against Ukrainian UAV attacks.
We note that Russia’s armed attack on Ukraine would also preclude Russia’s reliance on self-defense as a circumstance precluding wrongfulness (ASR, art. 22), for the UN Charter (art. 51) recognizes no right of self-defense against lawful acts of self-defense. Accordingly, there is no circumstance precluding any wrongfulness of the Russian actions.
Sovereignty Violations?
Under customary international law, as codified in Article 1 of the Chicago Convention, “every State has complete and exclusive sovereignty over the airspace above its territory” (see also DoD Law of War Manual, § 14.2.1.1). Similarly, the International Court of Justice (ICJ) has observed that the “basic legal concept of State sovereignty in customary international law, expressed in, inter alia, Article 2, paragraph 1, of the United Nations Charter, extends to … the air space above [a State’s] territory” (Paramilitary Activities, ¶ 212). This being so, a State that penetrates another State’s airspace in the absence of a “circumstance precluding wrongfulness” commits an internationally wrongful act.
Accordingly, it is irrefutable that Russia violated the territorial sovereignty of the Baltic States because its EW actions directly caused the UAVs to cross into their national airspace. The damage caused by the UAVs on Latvian and Estonian territory compounds the sovereignty violation (see discussion in Tallinn Manual 2.0, commentary accompanying Rule 2).
Since sovereignty violations do not require intent, this is the case regardless of whether Russia intended to divert UAVs into Baltic airspace or did so accidentally. Moreover, the fact that the UAVs were uncrewed military platforms has no bearing on whether the penetrations qualified as sovereignty violations. Although Article 3 of the Chicago Convention excludes State aircraft, such as military aircraft, it does not render the customary rule of sovereignty inapplicable. And Article 8 of the Convention, which likewise parallels customary law, expressly provides that “[n]o aircraft capable of being flown without a pilot shall be flown without a pilot over the territory of a contracting state without special authorization by that state and in accordance with the terms of such authorization.” The fact that Latvia issued a diplomatic protest confirms the absence of consent.
The possibility that the UAVs may have been equipped with AI capabilities that led to the airspace penetrations might be seen as an obstacle to Russia’s responsibility if the penetrations were unforeseeable. It is not. Since intent is not an element of a sovereignty violation, it is, therefore, also irrelevant whether the effects of EW countermeasures were foreseeable. Instead, as long as the EW countermeasures remained a significant element in a chain of causation that materially contributed to incursions into Baltic States airspace, Russia’s resort to them constitutes a breach of sovereignty.
Use of Force Violations?
The prohibition on the threat or use of force by one State against another is set forth in Article 2(4) of the UN Charter: “All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.” It is undoubtedly customary in character (Paramilitary Activities, ¶ 188).
The threshold issue is whether the incidents in question fall within the scope of the term “use of force” as understood in contemporary doctrine and State practice. Clearly, the prohibition includes acts that cause physical damage or injury. For instance, the Virginia-Georgetown Manual on the jus ad bellum confirms that while “There is no categorical definition of ‘force’ for the purposes of Article 2(4)….[i]n the final analysis, force means (at a minimum) coercive conduct producing destructive physical consequences, usually through violence” (p. 36). It cautions, however, that “a de minimis threshold is consistently observed, in general, as a matter of State practice.”
The physical damage in Latvia and Estonia certainly exceeded that threshold. In Latvia, multiple oil tanks were damaged, and a fire ensued, whereas in Estonia, the UAV crashed into the chimney of a power station. In our estimation, those two incidents clearly cross the use of force threshold. As noted in the UN General Assembly’s Definition of Aggression Resolution, “[b]ombardment by the armed forces of a State against the territory of another State or the use of any weapons by a State against the territory of another State” qualifies as aggression, which the resolution defines by reference to Article 2(4) of the Charter (art. 3(b)). The fact that Ukrainian UAVs were the means by which the force was delivered has no bearing on whether the material element of the use of force prohibition has been satisfied.
The more problematic question is whether the other airspace incursions, which caused no damage or injury, constitute a use of force. As a general matter, reconnaissance flights over another State’s territory have not been treated as such. For instance, in Paramilitary Activities, the ICJ treated U.S. reconnaissance overflights of Nicaragua as a violation of sovereignty, not a use of force (¶ 292).
However, in the present cases, the platforms that penetrated the airspace were armed military UAVs. Their presence, therefore, entailed a capacity for violence that exceeds that of ISR platforms. In this regard, a minority of the Tallinn Manual 2.0 International Group of Experts took the position that “the mere presence of a foreign military aircraft affecting the national security interests of the subjacent State, without the consent of that State, constitutes an armed attack per se” (p. 264). Since the prevailing view is that “armed attacks” are the “most grave form” of a use of force (Paramilitary Activities, ¶ 191), it follows that, at least for these experts, penetrating the Baltic State’s national airspace with Ukrainian UAVs would amount to a use of force. That the incidents occurred while a war is underway along the three States’ borders, and those States openly support Ukraine, provides additional context for that characterization.
In our view, both positions find some support in existing doctrine and are reasonable. But considering the totality of the circumstances, we lean towards the latter.
The more challenging legal issue is whether intent is an element of a wrongful use of force. Neither Article 2(4) of the UN Charter nor the Definition of Aggression Resolution addresses intent, leaving room for competing interpretations. One view is that, since intent is not explicitly required in the prohibition, the incursions amount to use of force violations regardless of whether they were intentional or unintentional.
We are of the view, however, that the requirement that the use of force be “against” another State implies a purposive element. On this reading, unintended effects on a third State’s territory do not constitute a use of force. After all, the purpose of the prohibition is to prevent States from employing armed force as a coercive, punitive, retaliatory, or otherwise malicious tool against other States. It is designed to deter a State from making a policy choice to use force.
Consistent with this approach, stray munitions, malfunctioning missiles, and navigational errors have generally not been treated as uses of force against the States whose territory they inadvertently enter. Applied to the present facts, if Russia was conducting defensive EW directed at Ukrainian UAVs, a lawful measure under the law of armed conflict (LOAC), and the Baltic airspace penetration and property damage were unintended byproducts of those operations, a colorable argument can be made that Russia did not use force “against” the Baltic States.
That said, foreseeability of the consequences is a relevant consideration under the purposive reading of Article 2(4). If Russia knew or reasonably should have known that its EW operations were likely to redirect armed Ukrainian UAVs into neighboring States, and nevertheless failed to take precautionary measures or issue warnings, this would indicate conscious disregard for the consequences, at least some of which were at the use of force level. It would be reasonable to treat such wilful disregard as satisfying the purposive approaches’ condition that the act be “against” the Baltic States.
A separate and more demanding question is whether the UAV intrusions and resulting damage rise to the level of an “armed attack” triggering the right of self-defense under Article 51 of the UN Charter and customary international law. In its Paramilitary Activities judgment, the ICJ held that only “the most grave forms of the use of force” constitute armed attacks (¶ 191). For instance, in its Oil Platforms judgment, the ICJ declined to confirm that the mining of a U.S. warship rose to that level (¶ 72).
Applying that threshold, the incidents fall short. However, we hasten to add that the United States has taken the view that all uses of force constitute armed attacks, thereby opening the door to forcible defensive responses (DoD Law of War Manual, § 1.11.5.2). Under its approach, at least the two incidents involving property damage would qualify as armed attacks.
This does not leave the Baltic States without recourse. International law recognizes the right of States to use force to prevent unauthorized penetration of their territory or to protect persons and property under domestic law, a right grounded in international law’s recognition of a State’s “enforcement jurisdiction.” And at a lower level of response, the fact that the Russian actions qualified as internationally wrongful acts on one or more grounds means they opened the door to legal, albeit non-forcible, countermeasures, that is, actions that would be unlawful but for the fact that they are designed to cause Russia to desist and provide reparations (ASR, ch. II).
Neutrality Law
Under the law of neutrality, “the territory of neutral Powers is inviolable” (1907 Hague Convention V, art. 1). As the DoD Law of War Manual notes, “[t]he inviolability of neutral territory prohibits any unauthorized entry into the territory of a neutral State, its territorial waters, or the airspace over such areas by armed forces or instrumentalities of war” (§ 15.3.1.1) This inviolability includes a prohibition on exercising “belligerent rights” on neutral territory. The Manual explains that the prohibition “requires belligerent forces to refrain from committing hostile acts” on neutral territory (§ 15.3.1.2). Thus, if Russia deliberately diverted the Ukrainian UAVs into the Baltic States’ airspace, the operations would undeniably violate their neutrality.
Matters become more complicated if they were not meant to have that consequence, as if they were an unintended result of jamming. The International Group of Experts that drafted Tallinn Manual 2.0 wrestled with this question in the cyber context. They agreed that if effects from operations in belligerent territory spilled over into neutral territory were unforeseeable, there was no violation of the law of neutrality. Regarding foreseeable consequences, the group noted that the law of neutrality seeks to balance belligerents’ right to conduct their military operations effectively with the neutral’s right to remain relatively unaffected by the conflict. Accordingly, when effects are foreseeable, “[e]ach case must be assessed on its own merits by balancing these competing rights” (Tallinn Manual 2.0, p. 554).
Applying this approach mutatis mutandis to UAV intrusions, it is significant that conducting GNSS spoofing or jamming against UAVs operating near neutral States increases the likelihood that those systems will penetrate their airspace. Russian EW operators must at least have been aware of the risk during the May incidents, if not before, since the March incidents should have alerted them to the possibility of such consequences.
Therefore, the question is how the balancing framework plays out. On the one hand, protecting Russian infrastructure from Ukrainian air attacks is an important interest, but so too is being free from both the penetration of one’s territory and the risk of physical harm, as occurred in two instances. This is a close case, and greater factual granularity, such as whether there were alternatives for defending the infrastructure, would be helpful. But immunizing neutral territory from the risk of physical damage or injury lies at the very heart of the law of neutrality, and in this case, should prevail. Thus, our view is that even if the penetrations were unintended, their foreseeability would support a finding of a neutrality violation.
International Armed Conflict?
If the UAV incursions did not violate the law of neutrality, the question arises whether they instead triggered an international armed conflict (IAC) between Russia and the affected Baltic States. Even when conduct violates jus ad bellum or neutrality rules, it does not automatically follow that an armed conflict was initiated (on the initiation of IACs, see Mike’s recent analysis).
Common Article 2 of the 1949 Geneva Conventions, which serves as the touchstone for determining whether an armed conflict exists, sets forth several bases for such a determination. Of relevance here, an international armed conflict occurs when there is “armed conflict … between two or more of the High Contracting Parties, even if the state of war is not recognized by one of them.” In Tadić, the International Criminal Tribunal for the former Yugoslavia further clarified that “an armed conflict exists whenever there is a resort to armed force between States” (Jurisdiction, ¶ 70). As States are involved, the question is whether the materiel condition of armed force is satisfied.
In this regard, the intensity of operations is not determinative. The 2025 ICRC Commentary to Geneva Convention IV emphasizes that “[i]t makes no difference how long the conflict lasts, or how much slaughter takes place” (¶ 306). The United States is in accord, noting that “any situation in which there is hostile action between the armed forces of two parties, regardless of the duration, intensity, or scope of the fighting,” qualifies as an IAC (DoD Law of War Manual, § 3.4.2).
Accordingly, if Russian forces intentionally diverted the UAVs into the airspace of neighboring States with a view to causing harm, such conduct would constitute a resort to armed force against those States and, as such, would trigger an IAC. But mere airspace penetration, standing alone and without some tangible form of harm, would not, even if the diversion was intentional.
This leaves the question of whether operations that caused physical damage initiated an IAC if unintentional. In other words, can such a conflict occur in the absence of “belligerent intent?”
Over time, the requirement for “animus belligerendi” has faded; today, the emphasis is on the factual existence of hostilities. But this does not mean that every act by one State that causes physical harm to another can be interpreted as “hostilities.” On the contrary, the aforementioned Tadić standard contemplates a “resort” to armed force by one State against another, which implies some degree of purposive conduct. If the UAV penetrations were purely unintentional byproducts of Russian forces defending against Ukrainian UAV attacks, it is difficult to characterize those actions as a resort to force against another State. Not only is there no belligerent intent, but there is no intent at all.
Concluding Thoughts
Except for the sovereignty and neutrality law violations, the legal classification of these incidents hinges on questions of intent–precisely where the facts remain thinnest. If Russia deliberately redirected the UAVs into Baltic airspace, the analysis is relatively straightforward: the conduct would be attributable to Russia under State responsibility, violate the sovereignty of the affected Baltic States, amount to a use of force in some of the incidents, and violate Russia’s obligation under the law of neutrality.
But if the incursions were unintended byproducts of Russian EW measures directed at Ukrainian UAVs–particularly if AI-enabled navigation contributed to the UAVs’ ultimate trajectory–the legal analysis becomes considerably more unsettled. The relevant question is no longer simply what occurred, but what Russia intended, knew, foresaw, or reasonably should have foreseen when deploying those countermeasures.
The technical complexity of GNSS spoofing, jamming, and AI-enabled navigation compounds uncertainty. These systems do not always produce linear or easily traceable effects, and the same EW measure may yield different operational consequences depending on the design and behavior of the affected UAV. In that context, intent cannot be mechanically inferred from outcome alone. The available facts do not yet permit a confident determination of whether Russia acted deliberately or recklessly, or merely engaged in lawful defensive operations whose effects spilled over into neighboring States.
Thus, the UAV incidents sit at the intersection of two enduring principles: a belligerent may defend itself against enemy operations, but it may not shift the resulting risks onto neutral States without legal consequences. As armed conflict increasingly involves EW, autonomous functions, and cross-border technical effects, that boundary between them will be harder to enforce—but no less important to maintain.
