 Some philosophers, however, seek a more robust defence of Combatant Equality. The three most prominent lines are institutionalist. A contractualist argument (Benbaji 2008, 2011) starts by observing that states (and their populations) need disciplined armies for the purposes of national defence. If soldiers always had to decide for themselves whether a particular war was just, many states could not raise armies when they need to. They would be unable to deter aggression. All states, and all people, benefit from an arrangement whereby individual combatants waive their rights not to be killed by one another—allowing them to obey their state’s commands without second-guessing every deployment. Combatants tacitly consent to waive their rights in this way, given common knowledge that fighting in accordance with the laws of war involves such a waiver. Moreover, their assent is “morally effective” because it is consistent with a fair and optimal contract among states.