Why do states formally invoke the right of individual self-defense? Legal-, diplomatic- and aid-politics to motivate states to respect international law

The use of force is prohibited under the UN Charter. An exception is written in Article 51, which allows a state to conduct an act of self-defense. This study explains why only some states invoke it. The author claims that the baseline probability of claiming the right remains low because explicit reference to Article 51 accompanies the uncertainty of justification success and poses legal and diplomatic costs. However, balanced escalation and no alliance relationship negate those costs and increase the likelihood of self-defense justification. Moreover, under the strict conditionality, minor powers receiving American military aid frequently and promptly claim self-defense.