Intervention by invitation and collective self-defence: two sides of the same coin?

intervention by invitation and collective self-defence are often dealt with as two distinct justifications to the prohibition of the use of force, thus two separate reasons for states to use force lawfully. Upon closer scrutiny, however, the two concepts appear to be quite similar as both deal with a situation where a state invites/requests the military assistance of another state. This article analyses both concepts and their criteria. It subsequently determines whether they are substantially different or in fact two sides of the same coin.