Is the judgment of a judge appointed by the Khawarij valid?
General Chapter
Al-Mughni
Book of Fighting Rebellious Groups
Primary text
The judgment of a judge appointed by the Khawarij is not valid because the minimum condition for them is sinfulness (fisq), which disqualifies one from judging.
Supporting text
It is plausible that his judgment may be upheld to avoid great harm and disruption arising from invalidating many judgments and contracts (including marriages) made over a long period, similar to the justification for accepting their collection of Hudud, Jizya, and Zakat.