What is the ruling regarding a person who kills a rebel when killing them is forbidden?

Primary text

If a person kills someone whom it was forbidden to kill, he is liable for compensation because he killed a protected life whom he was not ordered to kill. There are two views regarding retribution (qisas): the correct view is that retribution is not obligatory because there is a difference of opinion among the Imams regarding the killing of rebels, which constitutes a legally ambiguous situation (shubha) that repels the mandatory nature of retribution.