The Ruling on Referring to Anything Other Than the Law of Allah

Question:
There are tribes in the desert who, after the judge has ruled between the two parties, appoint people to judge between them with a ruling other than the ruling of the Shari'ah. They say, "This is an old custom of ours." What is the ruling on these people?

Answer:
They have no right to do that. It is not permissible for them to judge by anything other than the Law of Allah. Whoever is satisfied with that has committed disbelief—may Allah protect us from it. Whoever is satisfied with referring to anything other than the Law of Allah, and considers it better than the Law of Allah, or considers it permissible, or considers it good, or something similar to that, as mentioned in the three categories, becomes a disbeliever. Whether he is satisfied with it and considers it better than the Law of Allah, or equal to the Law of Allah, or permissible but the Law of Allah is better, all of this makes him a disbeliever.
It is obligatory for all Muslims to submit to the ruling of Allah, not to the ruling of the judge, for the judge may err or be correct. They must judge by the ruling of Allah in the matter itself. However, if the judge rules against them with something, and they mutually agree to forgive part of it—for example, the judge rules that Zayd must give 'Umar one thousand riyals, and they agree that the one in whose favor the ruling was made forgives five hundred—there is no harm in that. It is a settlement between them.