Q: What is your opinion on Muslims who judge by positive (manmade) law when we have the Qur'an and the Sunnah?
But no, by your Lord, they can have no Faith, until they make you (O Muhammad ﺻﻠﻰ ﺍﷲ ﻋﻠﻴﻪ ﻭﺳﻠﻢ) judge in all disputes between them, and find in themselves no resistance against your decisions, and accept (them) with full submission.
And whosoever does not judge by what Allâh has revealed, such are the Kâfirûn (i.e. disbelievers of a lesser degree as they do not act on Allâh's Laws). And whosoever does not judge by that which Allâh has revealed, such are the Zâlimûn (polytheists and wrongdoers of a lesser degree). And whosoever does not judge by what Allâh has revealed (then) such (people) are the Fâsiqûn [the rebellious i.e. disobedient (of a lesser degree) to Allâh].
Consequently, those who judge by laws other than the Shari'ah, and feel that this is permissible for them, or that it is better than judging by the Shari'ah, have undoubtedly by this stepped out of the circle of Islam. By reason of this, they are considered as Kafirs (disbelievers), wrongdoers, and Fasiqs (those who flagrantly violating Islamic law), as stated in the previous Ayahs (Qur'anic verses) and others, including Allah's Saying:
Do they then seek the judgement of (the days of) Ignorance? And who is better in judgement than Allâh for a people who have firm Faith.
May Allah grant us success!