So Parliament is to debate if it should authorise the government to use the RAF to bomb ISIS in Syria. What we must keep in our mind is that we i.e. the British state must only act under the rule of law. While the UN resolution (SC 2249) last week makes military action more likely to be legal, the legality still depends upon the actions to be taken. Many argue that the UN security council resolution changes nothing, because it does not authorise the use of military force under Chapter VII of the UN Charter.
Any actions need to remain an effective act of self-defence.