What's the name of the agreement allowing free passage across northern European borders including the one between Finland and Sweden?
Nordic Passport Union: The Nordic Passport Union allows citizens of the Nordic countriesIceland, Denmark, Norway, Sweden, and Finlandto travel and reside in another Nordic country (excluding Greenland and Svalbard) without any travel documentation (e.g. a passport or national identity card) or a residence permit.
i don't know