Some countries have an agreement with each other where the passport check isn’t required. For instance I believe Norway and Sweden have one because they are par

Some countries have an agreement with each other where the passport check isn’t required. For instance I believe Norway and Sweden have one because they are part of the Nordic Passport Union: https://en.m.wikipedia.org/wiki/Nordic_Passport_Union https://en.m.wikipedia.org/wiki/Nordic_Passport_Union