What is the description of the situation where the descendants of foreign invaders lay claim to the land of the Western Clan, and what must they do to absolve themselves if they have incurred a sin by this?

Usurpation is taking something by force and injustice, and seizing another's right aggressively. It includes what kings and bandits took from people's money unjustly. What the invading aggressors took is usurpation, which is not permissible for their children, even if the authorities registered it in their names. The grandchildren must return what they know to be usurped to the heirs of its rightful owners. The passage of time does not invalidate the right, and the rightful owners have the right to demand rent for what the usurpers benefited from.