Assessing the Legality of Ukraine’s ‘Operation Spiderweb’ Drones Under Article 36 of Additional Protocol I
On 1 June 2025, Ukraine executed a bold and unprecedented military operation, codenamed "Operation Spiderweb," targeting Russian strategic bombers deep within Russian territory. Utilising over 100 one-way attack drones, Ukraine struck multiple airbases across five Russian regions, reportedly damaging or destroying approximately 41 aircraft including nuclear-capable Tu-95 and Tu-22M3 bombers.
These attacks were carried out using drones launched from containers smuggled into Russia on civilian trucks and positioned close to military airbases. Media reports have variously suggested that the drones were either First Person View (FPV) (i.e. human-controlled), autonomous or both. Given the technical challenges of establishing communications necessary for FPV over such vast distances for multiple operators, this analysis proceeds on the basis that drones employed some autonomous functionality including detect, identify, and attack the Russian bombers.
The use of autonomous weapons raises important questions regarding their legality under international humanitarian law (IHL), particularly in the context of Article 36 of Additional Protocol I to the Geneva Conventions.
Understanding Article 36: Legal Review of New Weapons
Article 36 of Additional Protocol I obligates states to determine whether the employment of a new weapon, means, or method of warfare would, in some or all circumstances, be prohibited by international law. This legal review process is crucial to ensure that new technologies, such as the drones used in Operation Spiderweb, comply with IHL , including the principles of distinction and proportionality.
Ukraine, as a party to Additional Protocol I, is bound by this obligation. The Ukrainian Ministry of Defence has developed a national system for the legal review of weapons as part of its acquisition process. This process, described in their Voluntary Report on the Implementation of IHL (2024), uses the following traditional legal review methodology.
An Article 36 Legal Review Analysis
Preliminary Assessment
The first step in an Article 36 legal review is to assess whether the object in question qualifies as a "new weapon, means, or method of warfare." While the specific definitions may vary by state, it is uncontroversial that the attack drones used in Operation Spiderweb would fall within the definition of a weapon, given their intended use to destroy military objectives.
The preliminary assessment would also indentify the weapon's "normal or expected use". In this case, media reports suggest that the drones were designed to autonomously locate, classify, and attack Russian long-range bombers, targeting military objectives rather than personnel. Details about the initial activation mechanisms (e.g., timers or proximity sensors), deactivation/ neutralisation mechanisms and whether the drones could engage other military objectives remain unclear. Additionally, it is uncertain if the drones operated independently or performed different roles, such as target designation or attack, in a coordinated swarm. A comprehensive legal review would require detailed information on intended use and technical specifications, including the type and quantity of explosives and the accuracy and reliability of the autonomous identification/ classification functions.
Specific Prohibitions and Restrictions
The review assesses whether the weapon is prohibited by specific international treaties or customary international law. Currently, there is no international treaty specifically prohibiting or restricting the use of autonomous weapons in armed conflict. There is also no evidence to suggest that the drones used prohibited weapons to achieve their effects.
General Prohibitions - Assessing Indiscriminate Effects
In the absence of specific prohibitions, the review considers whether the weapon is prohibited because is causes certain prohibited effects. The most relevant prohibition in this case is the prohibition against weapons that are, by nature, indiscriminate. This assessment is contextual, as a weapon may be indiscriminate in one operational environment (e.g. urban areas) but not in another (e.g. isolated military bases). A legal review would require technical data from testing to demonstrate the system's accuracy and reliability, considering the normal or expected use. If the drones were specifically designed for Operation Spiderweb, the analysis would focus on their ability to reliably identify and strike Russian bombers stationed on airfields.
The limited media footage suggests that the Russian bombers were on airbases and that the drones were capable of accurately striking their intended targets.
Autonomous Functionality and IHL Targeting Rules
If the drones used in Operation Spiderweb were truly autonomous, the legal review would need to consider the system's ability to conduct attacks in accordance with IHL targeting rules. This requires a detailed and contextual consideration of the operational and environmental circumstances in which the weapon is to be used. A functional approach to the legal review of autonomous weapons can facilitate this analysis.
A legal review would evaluate the drone's ability to distinguish between lawful targets (e.g., Russian bombers) and unlawful targets (e.g., civilian aircraft or personnel). It would also assess whether the drones can conduct proportionate attacks, balancing the concrete military advantage gained against anticipated collateral damage to civilians and civilian objects. Media footage suggests that the risk of collateral damage was low, given that the Russian bombers were located on military bases. Considering the significant military advantage of destroying strategic bombers, if there were risks of collateral damage, the use of surveillance and reconnaissance drones may have helped avoid potential harm to civilians or civilian objects.
If the drones were designed to attack a range of military objectives beyond the specific Russian bombers, their ability to do so would also be considered during the legal review.
Conclusion
A legal review will generally make one of several possible recommendations i.e. that the weapon is lawful, that the weapon is lawful but with restrictions to mitigate legal risk or that the weapon is unlawful. Based on the limited information available from media reporting, it is arguable that an Article 36 legal review would determine that Ukraine's attack drones used in Operation Spiderweb were lawful. This analysis is based on several assumptions regarding the drones' intended use and autonomous functionality, including their ability to distinguish between lawful and unlawful targets.
The development of new weapons technologies, such as Ukraine's attack drones, raises various IHL and international law considerations. Consequently, incorporating Article 36 legal review analysis at the earliest stages of development allows national IHL and international law requirements to be considered and integrated into the design process. This is the essence of the Lawful by Design initiative which seeks to bridge the gap between the development of new technology weapons and national legal review processes.
