I have a post over at LawFare on the war on ISIS. There I discuss the views of Michael Walzer and Jeff McMahan before advancing my own proposal. Here it is:

1. The international community—represented by an appropriate military coalition—has a just cause to wage war on ISIS. That just cause is twofold: (a) the right of humanitarian intervention aimed at saving the populations in Syria and Iraq that are presently victimized by ISIS, and (b) the right of self-defense in response to ISIS’ attacks elsewhere.
2. The Coalition should include ground troops, which should ideally be recruited from states in the region.
3. The Coalition should conduct the war in accordance with jus in bello, including the principle of proportionality. The Geneva Conventions are a reasonable approximation to such norms.
4. The immediate aim of the war should be to defeat ISIS and put an end to its rule in the region. The long-term end of the war should be to help local populations establish the political institutions that will secure peace, freedom from violence, the rule of law, and human rights, in a way that creates the conditions for freedom and prosperity and prevents the resurgence of ISIS or similar murderous organizations. The length of time required to achieve this second aim cannot be established in advance.
5. At home, states struck by terrorist violence should employ the tools of just policing in a manner consistent with civil liberties and due process. In particular, states may not employ the tools of war to confront domestic terrorists.
6. The war should be accompanied by a generous immigration policy, especially toward those who flee ISIS’s rule. In implementing this policy, states are of course entitled to exclude terrorists and criminals.