Is it permissible to inquire about the owner of the disputed land, and what should be done with the planted trees if the land is legally registered in the name of the mother of the husband's mother (mother-in-law)?

If the questioner knows with certainty that the land rightfully belongs to someone other than the person legally registered as its owner, and the rightful owner is unaware of this or unaware that she possesses testimony concerning his right, then she must bear witness for him. If he requests her to testify before a judge to prove his right, then it becomes obligatory upon her. As for the trees planted by the questioner's father-in-law on land that is not his, while he was aware of it, he must uproot them, level the land, and restore it to its original state. He must also pay a fair rental value for the land for the entire duration of the usurpation. If he was deceived by a seller, he should uproot his trees and seek compensation from the person who deceived him for the cost of the trees. In matters such as these, the final word rests with the Sharia judiciary.