Later , it came to be used as the title of certain Muslim rulers who claimed full sovereignty . They did not have to take orders from any higher ruler , without claiming the overall caliphate . Later , it came to be used as the title of certain rulers who claimed almost full sovereignty in practical terms ( i.e. the lack of dependence on any higher ruler ) , without claiming the overall caliphate , or it was used to refer to a powerful governor of a province within the caliphate .