Originally Posted by
Dave510
The 24 hour rule is a DOT regulation; I'm not sure why OP would assume it applies to all flights, even if they have nothing to do with the US.
Because DOT jurisdiction extends to foreign carriers which conduct activities in the U.S. It extends in particular to ticket sales in the U.S. by foreign carriers. So, for example, foreign carriers must display fares marketed in the U.S.
inclusive of taxes and fees; otherwise they would be in violation of the full fare advertising rule (14 C.F.R. Part 399.84).