Originally Posted by
channa
This is not quite accurate.
UA allows Caribbean/Mexico/Canada as part of their * Gold benefits. So, a UA *G may enter a US lounge with such a flight. Although a US *G on the very same itinerary may not enter.
In short, a Star Alliance airline is not allowed to restrict *G benefits from other carriers' Elites. They are, however, allowed to restrict benefits given to their own Elites.
This is a very minor nuance, and US agents get it wrong all the time, but if you persist and make them read the entry requirements, it is very clear that for UA *G cardholders, any int'l boarding pass will do. It also worked on my US trip earlier this year from PVR in the PHX US lounge. The initial agent denied me, but her coworker next to her corrected her, saying that UA*G was fine, but US*G was not (kind of ironic, I know).
It's the US *G cardholder entry requirements that have such Caribbean/Mexico/etc. restrictions in effect.