Full Idea
It is a necessary condition of liability to defensive attack that one be morally responsible for posing an objectively unjustified threat.
Gist of Idea
A person or state may be attacked if they are responsible for an unjustified threat
Source
Jeff McMahan (Killing in War [2009], 4.1.1)
Book Reference
McMahan,Jeff: 'Killing in War' [OUP 2009], p.157
A Reaction
This implies that one may not actually be doing the threatening (but merely ordering it, or enabling it). McMahan aims to have the same criteria for wartime as for peacetime. He denies Anscombe's claim that merely posing the threat is enough.