Fighting the Khawarij is within the authority of the ruler, not that of individuals
Machine translationRead the Arabic original
The questioner:
May Allah reward you. This questioner asks: What is the ruling on obeying the ruler in killing the Khawarij who are attacking or demonstrating?
The Shaykh:
No, only the ruler fights them; individuals do not fight them. It would lead to greater harm and chaos. It is not permissible except through the ruler, just as 'Ali (may Allah be pleased with him) fought the Khawarij. Yes.
The presenter:
May Allah reward you. This questioner asks: If the ruler sees...
The Shaykh:
'Ali fought them, and he was the Caliph (may Allah be pleased with him); he is the ruler. Yes.
May Allah reward you. This questioner asks: What is the ruling on obeying the ruler in killing the Khawarij who are attacking or demonstrating?
The Shaykh:
No, only the ruler fights them; individuals do not fight them. It would lead to greater harm and chaos. It is not permissible except through the ruler, just as 'Ali (may Allah be pleased with him) fought the Khawarij. Yes.
The presenter:
May Allah reward you. This questioner asks: If the ruler sees...
The Shaykh:
'Ali fought them, and he was the Caliph (may Allah be pleased with him); he is the ruler. Yes.
Source
قناة «العلامة الدكتور صالح الفوزان»، [3436/2993] قتال الخوارج من صلاحيات ولي الأمر لا آحاد الناس - الشيخ صالح الفوزان — youtube.com
The Arabic text is a machine transcription of the audio recording.