If they signed up because of this, boy I wouldn't want to be in their shoes once they realize their mistake! Judging by everything I read, ISIS rulers enforce a strict Sharia law, with patrols making sure everyone is using the correct dress code.

I've also seen a documentary with a woman going undercover into ISIS-held territory (I think it was by the BBC) which claimed that Jihadists that break the "law" get killed, and that in fact ISIS welcomes any reports of misbehavior of their troops and punishes them hardly. ISIS seems to be ruling their territory with an iron hand, it's definitely not the land of do as you please and kill whom you fancy.