Full Idea
Moral equality means either 1) because just combatants are permitted to fight in a just way, so are the unjust , or 2) because the just are justified, so are the unjust, or 3) because the just are justified, the unjust are therefore permitted.
Gist of Idea
Equality is both sides have permission, or both sides are justified, or one justified the other permitted
Source
Jeff McMahan (Killing in War [2009], 3.1.2)
Book Reference
McMahan,Jeff: 'Killing in War' [OUP 2009], p.110
A Reaction
[summary] McMahan calls 1) the weak version, and 2) the strong. He suggests that although 3) is unusual, it is what most people believe - that if the good are justified, the bad are permitted to fight back. He rejects them all.