The below answer may help;
If it is asked: who is it that should carry out this hadd punishment for zina? The answer is: No one should carry out the hadd punishments without the permission of the ruler. If there is no ruler who rules according to sharee’ah then it is not permissible for the ordinary people to carry out the hadd punishments. Whoever does that is sinning, because carrying out the hadd punishments requires examining the matter and requires shar’i knowledge in order to know the conditions of proof.
The ordinary people have no knowledge of such things, and the carrying out of one of the hadd punishments by the ordinary people leads to many evils and the loss of security, whereby people will attack one another and kill one another or chop off one another’s hands on the grounds that they are carrying out hadd punishments.
There is no dispute among the scholars that qisaas (retaliatory punishments) such as execution cannot be carried out except by those in authority who are obliged to carry out the qisaas and carry out hadd punishments etc, because Allaah has addressed the command regarding qisaas to all the Muslims, and it is not possible for all the Muslims to get together to carry out the qisaas, which is why they appointed a leader who may represent them in carrying out the qisaas and hadd punishments.
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