Is an act of murder considered legitimate if committed by an extremist based on a fatwa from an imam that deems the victim's blood forfeitable?

It is not possible to speak about an issue whose reality has not been clarified. Unlawfully taking a life is one of the gravest sins, and Allah has promised a severe punishment for its perpetrator; it is forbidden unless Allah has permitted it. The execution of a penalty upon one who deserves death is solely the responsibility of the ruler (Sultan) or his deputy (such as a judge), and no individual is permitted to carry it out, to prevent chaos. Issuing a fatwa (religious edict) is a matter of great peril, and the Mufti (one who issues fatwas) must investigate thoroughly and exercise caution, because speaking about Allah without knowledge is a grave sin, and it is the foundation of shirk (polytheism) and bid'ah (innovation), leading people astray, and the sin of issuing a fatwa without knowledge falls upon the Mufti.