When passports first emerged, there was no clear distinction between internal and international ones. Later, some countries developed sophisticated systems of passports for various purposes and various groups of population. Uses for the internal passports have included restricting citizens of a subdivided state to employment in their own area (preventing their migration to richer cities or regions) clearly recording the ethnicity of citizens to enforce segregation or prevent passing, and controlling access to sensitive sites or closed cities
I'm surprised Trump missed that one in his reform promises
"In a time of universal deceit telling the truth is a revolutionary act"