Originally Posted by
NickB
The traveler is supposed to have sufficient evidence to the satisfaction of the immigration officer, not just a "plausible story". The fact the legislation does not purport to exhaustively and definitively list what evidence is acceptable does not mean that there is no requirement to have any documentary evidence beyond a "plausible story".
There we go to the problem of "unclear rules".
While most things regarding immigration is clear, in the end any immigration officer can make it's own rules - and I've seen plenty of those myself.
A well-stamped passport (but still with enough space available to stamp) had me once almost denied entry into Singapore as the immigration officer said it was "too full" and that he'll let me in "just this time only". Needless to say, I used it to travel to another 7 or 8 countries afterwards (before having the possibility to get a new one at home) without any problems at all.
Plenty of cases where TWOV for China wasn't properly understood by CI agents too (not in China, but at checkin in Europe/Asia/US), with some being denied travel because of that.
And reports of hundreds of Swiss citizens every year alone turned away by US immigration are regularly hitting the newspapers locally.. must be thousands of Europeans alone that are sent back from the US, because US immigration officers "didn't liked something" on them. Pretty simple.. there is no "right" to be admitted into another country, even if you perfectly hold all documents.