The extent of the usurper's liability when the owner chooses to hold him liable for compensation.
General Chapter
Al-Mughni
Book of Usurpation
Primary text
If the owner chooses to hold the usurper liable, and the ruling is that liability for usurpation is equivalent to liability for the injury, the usurper is liable for half the value. The usurper then has the right to seek reimbursement from the perpetrator for that half-value, because the damage occurred through the perpetrator's action, establishing the primary liability upon him.
Supporting text
If the ruling is that liability for usurpation is based only on the resulting defect (what is lost in value), the owner may hold the usurper liable for the greater amount, as what is present in the usurper's possession is treated as part of its full value. The usurper then recovers half the value from the perpetrator, as this is the compensation for the injury caused by the perpetrator.