you're correct
http://blogs.abcnews.com/theblotter/2006/10/new_foley_insta.html
Maf54: we will be adjourned ny then
Teen: oh good
Maf54: by
Maf54: then we can have a few drinks
Maf54: lol
Teen: yes yes ;-)
Maf54: your not old enough to drink
Teen: shhh…
Maf54: ok
Teen: that's not what my ID says
Teen: lol
Maf54: ok
Teen: I probably shouldn't be telling you that huh
Maf54: we may need to drink at my house so we don't get busted
A 20 year old is not old enough to drink. But they're certainly an adult.
Reading this it could be possible that Foley didn't know for some time the kid was underage. The kid admits his ID says he's older than he really is.