cameron, at "the guardian" warns of dangerous precedent being set -- "the daily mail" is backing .ameron cameron justified the killings as an act of self-defense under article 51 of the united nations charter, the first time the clause has been invoked for a targeted killing. amid questions over the legality of this broader interpretation of self-defense, the british defense secretary insisted it would be the way of things to come. >> there are other terrorists involved in other plots that may come to fruition over the next few weeks and months, and we would not have to take similar action again. reporter: cameron has said he supports bridge extending its bombing campaign against the islamic state group to syria -- he supports britain expanding its bombing campaign against the islamic state group to syria. anchor: let's address this debate with our guest from london, who joins us over the phone. you are a director of international security studies at the royal united services institute. purely from an operational perspective, how efficient are the east road strikes, how necessary are they for th