Originally Posted by
channa
This is not entirely correct.
For US lounges, they do not deny *G on Mexico/Canada itins. They only deny their own (US members) on Mexico/Canada itins. *A prohibits them from denying other *G members on int'l itineraries.
I have successfully entered US lounges on a US ticket to/from Mexico and a UA*G card. Some agents question it, but if they refer to their documentation, it's quite clear. A US member is to be denied, but a UA (and presumably CO in the future) member is not.
As a UA star gold, I've been turned away everytime by US lounges on a Caribbean (not PR or USVI) ticket at CLT. I suspect that you had luck going to Mexico via PHX.
I questioned it twice and the lounge dragon got belligerent, once waving a book at me. I haven't tried the last couple of times as nothing drags down the beginning of a vacation as a confrontation with a US lounge dragon.
It's against the rules. It's not right but it happens and happens often. Citing the Star Alliance rules does no good. YMMV