&gt;as Hollande has claimed France is at war with IS<p>France would still be subjected to international law.  So let&#x27;s watch where this concept of war with non-state actors breaks down.<p>1.  IS is responsible for the use of armed force violating France&#x27;s territorial integrity.<p>2.  France responded with use of force (bombing) against IS targets in Syria, violating Syria&#x27;s territorial integrity.<p>You see there is no IS territorial integrity, that is the problem with being a non-state actor.  Although France was attacked by IS, France can not follow IS any where it likes.<p>So the legal question is:<p>1.  Did France have a lawful right respond with the use of force against IS in Syria?<p>Likely yes, because: a.) some of the individuals most responsible for the acts in Paris and potentially planning future attacks are operating in Syria; and b.) Syria is not likely to stop IS attacks from originating within its own borders.<p>Now lets take the extreme example of a potential IS teenage recruit in the US, do you think France will lawfully be able to bomb the IS recruit in US borders under those facts?  Not likely.<p>Take the middle of the road real life response in Belgium, where some of the Paris attack planning may have originated, notice France did not bomb in Belgium like in Syria and instead worked with Belgium to do police style raids.<p>2.  Was France&#x27;s response (bombing) proportionate to IS&#x27;s use of force?<p>I don&#x27;t think there will be many who argue France&#x27;s use of armed force was disproportionate to the Paris attacks (someone will), but in the case of IS you see where it could be a slippery slope.  Hypothetical: the <i>mastermind</i> could be hidden among an otherwise entirely civilian population, and if it were shown bombing killed thousands of civilians to get 1 IS member there may be some issues of proportionality.