A firman or ferman at the constitutional level was a royal mandate or decree issued by a sovereign in certain historical Islamic states, including the Ottoman Empire, Mughal Empire, State of Hyderabad, and Iran under Shah Mohammed Reza Pahlavi. During various periods they were collected and applied as traditional bodies of law. The word firman comes from the Persian: farmân (فرمان) meaning "decree" or "order". In Turkish it is called a ferman.
On a more practical level, a firman was, and may still be, any written permission granted by the appropriate Islamic official at any level of government. Westerners are perhaps most familiar with the permission to travel in a country, which typically could be purchased beforehand, or the permission to conduct scholarly investigation in the country, such as archaeological excavation. Firmans may or may not be combined with various sorts of passports.
Read more about Firman: Origins of Firmans in The Ottoman Empire, Organization, Other Firmans, Other Uses