What is the ruling on selling Rikāz (buried treasure) in a country whose laws criminalize its sale, even though it is Islamically permissible? And is it obligatory to inform other heirs if it is found in inherited land? And what is the ruling on selling the land if the buyer knows of the presence of Rikāz in it and will excavate it?

Whoever finds a rikaz (buried treasure) must extract one-fifth of it, for the Prophet, peace and blessings be upon him, said: "One-fifth is due on rikaz." The rikaz found in inherited land is divided among the heirs. It is not permissible to sell rikaz along with the land, nor to sell it while it is still in the ground, because its quantity is unknown. However, once it is extracted and its quantity is known, it is permissible to sell it after one-fifth has been taken out. If sold for cash, immediate possession (of the cash) is a condition.