Answer:
If someone’s family member does an act contrary to the teachings of Islam, then it is his responsibility to amicably stop the person from violating the injunctions of the Shariah and to advise him/her.
A person who accuses another of committing adultery and cannot bring four witnesses who clearly saw the act taking place, is guilty of falsely accusing someone of adultery, the punishment for which is being flogged with eighty stripes. (This punishment, too, is to be carried out by the Court).
Allah, the Exalted, says:
Flog those who accuse any of the chaste women (of committing adultery), but fail to backup (their charges) with four eyewitnesses — flog them with eighty lashes, and thereafter do not accept their testimony ever again. Surely, they are the wicked ones. (Quran 24:4)
According to Islam, the punishment for wrongfully killing someone is very severe:
If a man kills a believer intentionally, his recompense is Hell, to abide therein (For ever). And the wrath and the curse of Allah are upon him, and a dreadful penalty is prepared for him. (Quran 4:93)
In short, honour killing is not permitted according to Islam. Encyclopaedia Britannica has correctly stated:
“Such “honour killings” are in fact violations of both civil and Islamic law, but perpetrators frequently use religious reasons to defend their actions, thereby giving the crime a veneer of justification.”[i]
Mufti Faizal Riza