> Most countries recognize very different limits at a customs boundary. In the US I've heard that boundary (the "border") encompasses ~75% of everyone living i

> Most countries recognize very different limits at a customs boundary. In the US I've heard that boundary (the "border") encompasses ~75% of everyone living inside. It's like "within X miles of a border" and includes rivers and airports as well as the entire coastline. I'm not up to date on these rules and who's been caught out by them, but I have repeatedly heard the claim above.