When aid or assistance in the use of force turns into an indirect use of force

This article explores when aiding or assisting another state in the use of force against a third state may turn into a ‘use of force’ within the meaning of Article 2(4) of the UN Charter. The provision of weapons to a belligerent state is usually not considered to pass this threshold. But one can imagine extreme cases where it is appropriate to assume that Article 2(4) is implicated. This article argues that a contribution that directly materialises in another state’s direct use of force against a third state, and is essential to that use of force, should be treated as an indirect use of force if the contributing state itself intends to force the will of the third state. Military support to Ukraine has come to a point where these criteria would be met.