The Australian government is considering a U.S. request, possibly engineered from Canberra itself, for participation in the air campaign against the Islamic State in Syria. No one doubts the abhorrent and repellent ideology and murderous practices of IS. But prime ministerial warnings of IS being "a death cult" whose members "are coming after us" is emotive fear-mongering: No nation can go to war on mere slogans. Due diligence requires that the evaluation be done with sympathy tempered by caution and humility.

The legal justification for bombing raids without Syrian government consent is dubious. The laws of war, as enumerated authoritatively in the U.N. Charter, restrict the international use of force by all countries to just two narrow circumstances: self-defense against an armed attack and when asked for or authorized by the U.N. Security Council. Even the responsibility to protect (R2P) principle requires prior Security Council authorization and is not a substitute for U.N. (in)action.

Efforts to rescue and protect at-risk victims of IS slaughter and sexual enslavement trapped in pockets of Iraqi territory, for example the Yazidis, with Iraqi government permission were a good demonstration of R2P in action. Widening the theater of operations into Syria against its government's wishes would violate a core R2P procedural requirement.