Question To Shaikh Al-Islam Ibn Taymiyyah (rahimahullāh, d. 728H): It is concerning a woman who has been accused by her people, so they beat her, and imprisoned her and wanted to kill her―are they allowed to do that?
Answer: “All praise is for Allah! It is not permitted for them to kill her even if they are certain that she has committed adultery because the Prescribed Punishments (Hudūd) are not for anyone to carry out except the Ruler or whoever he has appointed. So, they must protect her and keep her safe. And Allah knows best.”
(See Majmū’ Al-Fatāwā 34/178.)
The punishments prescribed in the Sharī’ah cannot be carried out by individual citizens of a nation (or groups of them). The duty of carrying out the hudūd lies with the ruler and those he has appointed such as the judges and police etc. If the ruler does not carry out the hudūd as he ought to, then the role is not transferred to the citizens. In that situation, it is upon them to be patient―and they can use the law of the land to attain justice to the degree that is possible but without transgressing the Laws of Allah.