ISIL is putting a senior religious advisor, a Saudi cleric, on trial for openly criticizing the ISIL leadership for executing a captured Jordanian pilot by burning him alive. The cleric declared that such a method of execution was not Islamic and that those who carried it out should be put on trial. ISIL leadership decided to try the cleric on trial instead, for bad behavior, and may execute the man. This is all because in early February ISIL got a lot of publicity when it released the video of them burning to death of a captured Jordanian pilot.
Outside of ISIL the reaction was generally revulsion and calls for revenge. ISIL seemed to relish that and the use of this form of execution (which used to be popular in the West centuries ago). It was first believed that everyone in ISIL also approved of stuff like this, as well as the use of crucifixion, beheading or stoning for executions. Apparently not and it soon became apparent that there are a growing number of critics to these barbaric methods within ISIL. Many lower ranking ISIL men were put off by this execution. The full extent of this dissent will only be known when more disillusioned ISIL veterans return home. Those lower ranking ISIL men who object to the burning knew to keep quiet about it, because a quick, quiet execution follows discovery of such disloyal attitude among the rank and file. But when more senior ISIL men object, especially if the critic is a religious advisor, one must be more careful. In the few cases so far the offending official was still executed, but the trial enables ISIL to explain why this guy got so high in the organization only to eventually face execution.
Internal criticism is not the only problem ISIL faces as the Islamic terror group is not doing well so far this year. They admitted their defeat by Kurds at Kobane and the Syrian Army is retaking ground as well. The Kurds are also defeating ISIL forces near the Iraq border and in Iraq Kurds, Iraqi soldiers and Sunni and Shia militias are both stopping ISIL attacks and pushing back ISIL forces in a growing number of areas. An offensive to retake Mosul is expected before June. Meanwhile air attacks not only continue but are more frequent. This makes it more difficult to stockpile supplies or move large numbers of gunmen.
More of the people in ISIL controlled territory are rebelling or otherwise showing their displeasure at ISIL rule. To make this worse ISIL has taken to conscripting people for their armed forces or simply to do manual labor. The only area where ISIL is advancing is in Internet propaganda and now even that is being criticized both inside and outside of ISIL.