From March 25, 2001, the Schengen acquis fully applied to the five countries of the Nordic Passport Union (except for the Faroe Islands, which remain outside the Schengen area). Border checkpoints have been removed within the Schengen zone. There are some areas in the Nordic Passport Union that gives extra rights for Nordic citizens, not covered by Schengen, such as less paperwork if moving to a different Nordic country, and fewer requirements for naturalisation of citizenship. Within the Nordic area any Nordic ID card, (e.g. a driving licence) is valid for Nordic citizens, because of the Nordic Passport Union, while a national ID card or a passport is required in other Schengen countries. Most Scandinavian people do not own any Schengen approved national ID card, so they need a passport when visiting Schengen countries outside the Nordic area.
Before 2001, the principle was for land and ferry travel that there were full customs check when travelling from Denmark into the other countries. Passport was not supposed to be needed for Nordic citizens, but could be useful for those not speaking a Scandinavian language natively. Every car driver was asked about where they have been, and suspicious people were checked further. For land and ferry travel into Denmark and between Sweden/Norway/Finland there were much more relaxed customs and passport checks, often no check at all. For air travel there were full passport and customs check, even though verbally claiming Nordic citizenship with a Scandinavian language, plus showing the ticket for the intra-Nordic flight, or any Nordic ID card was usually enough to pass the passport check. Passengers travelling by public transport such as train or air were usually not interviewed.
From March 2001, the Schengen rules have given more relaxed customs checks from Denmark, and also no passport checks on airport, since intra-Schengen travellers are separated from the travellers from outside the Schengen area.
