Providing Weapons to Ukraine: The First Exercise of Collective Self-defence by the European Union?

The European Union's decision to supply weapons and military equipment to the Ukrainian army, which is engaged in repelling Russian aggression, could amount to an international use of force, albeit minoris generis. In this case, the question arises as to whether it is admissible under international law on the use of force. One possible legal basis is the legal regime of collective self-defence. However, according to the classical interpretation, international law only grants States the power to act in self-defence, and the assistance benefiting Ukraine provided under Council Decision 2022/338 does not seem to be attributable to the EU Member States, even if they have brought weapons onto Ukrainian territory. On the contrary, military support for the Ukrainian army seems entirely attributable to the Union, which would have adopted the conduct of its Member States as States and international organisations might do with the conduct of individuals under international law of responsibility. This Article argues that the Council's decision to supply weapons to the Ukrainian army can be regarded as a first attempt to amend customary law, precisely to allow international organisations to act in collective self-defence in certain limited cases.