Just war theory is currently dominated by two positions. According to the orthodox view, provided that jus in bello principles are respected, combatants have an equal right to fight, regardless of the justice of the cause pursued by their state. According to “revisionists” whenever combatants lack reasons to believe that the war they are ordered to fight is just, their duty is to disobey. I argue that when members of a legitimate state acting in good faith are ordered to fight, they acquire a pro-tanto obligation to obey which does not depend for its validity on the justice of the cause being pursued. However, when the war is unjust, this obligation may be overridden, under certain conditions, by the obligation not to contribute to the unjustified killing of innocents. This is because the pro-tanto force of the duty to obey the law is best understood in terms of “presumptive”, rather than “exclusionary” reasons for action. This approach captures the insights of both the orthodox and the revisionist view, while avoiding the problems that afflict each of them.