Unfortunately it has courts, police, and a military. It has nearly 10 million citizens, and in articles about its territorial gains, it even appears on maps. It even collects taxes, repairs roads and runs electric utilities.
The sad reality is that it is both quintessentially Islamic, and a state. If we refuse to acknowledge the reality of the situation today, we have no chance of destroying it in the future.
It's court, police and military are not independent structures but the same bunch of armed militants. If controlling a territory with sword and fire is the criterion of statehood, we have a bunch of states right now on our hands, including Taliban State, Boko Haram State and 18th Street State.
I concur it's advantageous they are positioning themselves as a state though. It immediately translates their military defeats into social and political ones.