Just a theological question, by what legitimation does Ibrahim, the caliph proclaimed by ISIS draw his title from? From what I understand, the major inner conflict between muslim groups has been the question of by which mechanism the caliph should be chosen, with Schiits claiming it should be the successor of Mohammeds cousin (?) Ali and the Sunnits claiming he should be elected.
Now ISIS is Sunnit, right? Has there been any "election", or by what theological ground does ISIS and Ibrahim legitimise his position as Caliph?