Good heavens. I don't know how much truth there is in this kind of threat; it does bear watching, with both alarm but also a healthy dose of skepticism.
It does looks odd, on the surface at least. The US makes huge revenue from the tourist industry, and this legislation, if it does exist, given widespread publicity, would make a great many people uneasy about visiting the US. I imagine that the huge majority of Americans would be pissed (royally so), if they were to read about kangaroo court laws of this variety. What sort of people support this sort of legislation? And if so, what would be the justification for that support?
This is a counterproductive type of measure, if it indeed exists. The only way this sort of measure could ever be brought into play, and accepted without vigorous protest by the general public, would be another very large terrorist attack in the US. Dare one suggest that HSA "expects" an incident like this, and the law has already been prewritten to go into effect when the public will accept it? After all, that is exactly what happened with the "Patriot" Act... the bulk of which was drafted several months before the September 11 attacks, but never saw the light of day until a week or afterwards.