This comes up with school districts too. My home county in rural Ohio had a school district administration that oversaw all the schools in the county but there are two 'exempted' school districts. One is a town that is split between two counties, so the school district would fall in two counties. Hence it is "exempted" from both and the official name is "<TOWN NAME> Exempted Village Schools". The other one if the largest town in the county, which due to it's size voted to exempt itself from the services and administration of the county government, presumably since this single school has as many students as the rest of the county combined.