1) It should remain in consideration at the outset that the directive which contains Islamic punishments is addressed to the Muslims in their collective capacity and not in their individual capacity. This is an obvious fact. For this very reason, the surahs in which these punishments are mentioned were revealed in Madinah where a Muslim state had already been established under the rule of the Prophet (sws). Therefore, whatever collective system of Muslims is in place at any particular time, whether in the form of a democratic parliament or a tribal elective system etc., the decisions will be made by that authority.
2) The death sentence, according to the Quran, can only be given to a person who has killed someone or to someone who is guilty of spreading anarchy in the society (Muharabah/Fasad Fil Ard). The Almighty has made it amply clear that when the Israelites were given the shariah, He had ordained at that time that except for these two offences neither a person nor a government has the right to kill a person. The Quran says:
مَنْ قَتَلَ نَفْسًا بِغَيْرِ نَفْسٍ أَوْ فَسَادٍ فِي الْأَرْضِ فَكَأَنَّمَا قَتَلَ النَّاسَ جَمِيعًا
He who killed a human being without the latter being guilty of killing another or of spreading anarchy in the land should be looked upon as if he had killed all mankind. (Quran 5:32)
In today’s time where judiciary has become a pillar of that state and represents the collective system of a Muslim society under broader umbrella of the parliament, it’s not permissible to kill anyone until they have been proven guilty and deserving of capital punishment in the court of law.
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To understand Ghamidi Sahab’s stance in Detail, please refer to the following thread:
Discussion 27158