>>8044
Assuming OP is talking about fighting ISIS in the middle east:
>Just Cause
ISIS is persecuting christians, executing people, and is not providing for the common weal of their subjects.
They are causing violence and engaging in unjust war, so stopping them in the name of restoring peace is a just cause
>last resort
ISIS is not open to negotiation, and cutting their supply lines via economic sanction seems to be of no avail.
>legitimate authority
The pope is a sovereign of the vatican city state, so if he were to declare a crusade, it would be by the power vested in him as ruling sovereign of a nation.
>probability of success
Unknown. Currently, the pope has no standing army, so it would depend on who he could muster.
>right intention
overall, this is up to the pope. Does he wish to wage war to restore peace to the middle east, or does he wish to slaughter muslims for fun? This is a question only he could answer.
>proportionality
this is a question of jus in bello. Since we are not currently in bello, we cannot answer this one.
>civillians
again, a question of jus in bello. We have to go to war to see if this is met.