Sayyiduna Sa'b bin Jathamah (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings be upon him) said: "It is not permissible for anyone except Allah and His Messenger (peace and blessings be upon him) to declare a pasture (to prohibit grazing or hunting there)." (The caliph is also the representative of the Messenger of Allah, peace and blessings be upon him.)