Under what conditions can an appointed judge appoint a substitute (Istikhlaf)?
General Chapter
Al-Mughni
Book of Judiciary
Primary text
If the Imam grants the appointed judge permission to appoint a substitute, this delegation is permissible without any known disagreement. If the Imam explicitly prohibits the appointed judge from appointing a substitute, then he is prohibited from doing so because his authority stems from the Imam's permission, thus he cannot act against the prohibition, similar to a commissioned agent (Wakil). If the Imam grants the appointment without specifying the ability to appoint a substitute (i.e., leaves it unrestricted), then the judge has the authority to appoint a substitute.
Supporting text
An alternative view suggests that the appointed judge does not have the right to appoint a substitute unless explicitly permitted, as he acts based on permission and cannot do what was not authorized, analogous to a general agent. Proponents of the primary view argue that the purpose of judging is resolving disputes, which can be done by the judge himself or by a delegate, as if the Imam had permitted it. This differs from agency (Tawkil) because the Imam delegates the judiciary for the benefit of the Muslims, not for himself. If a judge appoints a substitute where he lacks permission, his judgment is considered as if it were rendered by someone who was never appointed.