ISIS arrested own judges for putting religion before politics, executes one
http://www.al-monitor.com/pulse/tr/security/2014/09/is-takfiri-caliphate.html#
http://www.spiegel.de/politik/ausland/islamischer-staat-koepft-seinen-schaerfsten-richter-a-1023127.html
(article in german)
The most important religious tool of ISIS is the practice of "takfir": A muslim can be declared an infidel and therefore enemy of Islam. ISIS is sunni and for waging war against the Shi'ites it's important to declare them infidels first.
One of ISIS' judges has been a little bit too... enthusiastic with takfir. Abu Jaafar al-Hattab was of the opinion that you can be declared an infidel even if you are not aware of your failings. Accordingly, Ayman al-Zawahiri, the leader of al-Qaeda, was declared an infidel for not sufficiently hating Shi'ites. Likewise all leaders of the Islamic Front and the Free Syrian Army, both rivals to ISIS.
This comes at a bad time when ISIS is in a power-struggle with other extremist groups (Ansar al-Islam, al-Nusra, Al-Qaeda) and has to forge alliances. A takfir-happy judge declaring potential allies for infidels is a roadblock in that.
This was in fall 2014.
Abu Jaafar al-Hattab has recently been executed.
Excerpt:
"While some believe that these developments indicate a reconsideration within the IS leadership aimed at limiting the phenomenon of takfir and excessive violence, especially since its implications started affecting the organization itself. Others believe there are no real reconsideration but rather that IS leaders believe that the current stage calls for mitigating violence and gaining the trust of the popular base. This is especially true since the coming days will be difficult, given the possibility of US strikes. Therefore, it is in ISs best interest to neutralize the populace to prevent it from cooperating with the new alliance being formed against IS both in Iraq and Syria."